diff --git a/README.md b/README.md
index fcd077d..ca1f9af 100644
--- a/README.md
+++ b/README.md
@@ -166,6 +166,8 @@ Code examples and usage can be found in [Usage.md](USAGE.md)
 
 If you prefer a step by step tutorial, you can read the article I wrote on [How to integrate Mpesa into your Laravel Application](https://www.iankumu.com/blog/laravel-mpesa).
 
+You can also find a [demo application](https://github.com/Iankumu/Payments) I created that uses the package. It provides a starting point on how to integrate Mpesa into a Laravel Application.
+
 ### Testing
 
 ```bash
diff --git a/src/Exceptions/CallbackException.php b/src/Exceptions/CallbackException.php
new file mode 100644
index 0000000..24cd8a5
--- /dev/null
+++ b/src/Exceptions/CallbackException.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace Iankumu\Mpesa\Exceptions;
+
+use Exception;
+
+class CallbackException extends Exception
+{
+    public static function make(string $callback, string $message = null): self
+    {
+        if (!is_null($message)) {
+            return new self("The {$callback} cannot be null. " . $message);
+        } else {
+            return new self("The {$callback} cannot be null.");
+        }
+    }
+}
diff --git a/src/Mpesa.php b/src/Mpesa.php
index 796a907..a381e27 100644
--- a/src/Mpesa.php
+++ b/src/Mpesa.php
@@ -2,6 +2,7 @@
 
 namespace Iankumu\Mpesa;
 
+use Iankumu\Mpesa\Exceptions\CallbackException;
 use Iankumu\Mpesa\Utils\MpesaHelper;
 use Illuminate\Http\Response;
 use Illuminate\Support\Carbon;
@@ -101,7 +102,7 @@ public function __construct()
      * @param int $phonenumber The phone number that will receive the stkpush prompt in the format 254xxxxxxxxx
      * @param int $amount The amount to be transacted
      * @param string $account_number The account number for a paybill
-     * @return object Curl Response from Mpesa
+     * @return \Illuminate\Http\Client\Response
      */
     public function stkpush($phonenumber, $amount, $account_number, $callbackurl = null)
     {
@@ -134,13 +135,13 @@ public function stkpush($phonenumber, $amount, $account_number, $callbackurl = n
                 'CallBackURL' => $callbackurl
             ];
         } else {
-            return response()->json([
-                'error' => 'Callback URL cannot be null'
-            ], Response::HTTP_NOT_ACCEPTABLE);
+            throw CallbackException::make(
+                'callback_url',
+                'Ensure you have set a Callback URL in the mpesa config file'
+            );
         }
 
-        $response = $this->MpesaRequest($url, $data);
-        return $response;
+        return $this->MpesaRequest($url, $data);
     }
 
     /**
@@ -149,7 +150,7 @@ public function stkpush($phonenumber, $amount, $account_number, $callbackurl = n
      * This method is used to check the status of a Lipa Na M-Pesa Online Payment.
      *
      * @param string $checkoutRequestId This is a global unique identifier of the processed checkout transaction request.
-     * @return object Curl Response from Mpesa
+     * @return \Illuminate\Http\Client\Response
      */
 
     public function stkquery($checkoutRequestId)
@@ -163,8 +164,7 @@ public function stkquery($checkoutRequestId)
 
         $url = $this->url . "/mpesa/stkpushquery/v1/query";
 
-        $response = $this->MpesaRequest($url, $post_data);
-        return $response;
+        return $this->MpesaRequest($url, $post_data);
     }
 
 
@@ -177,7 +177,7 @@ public function stkquery($checkoutRequestId)
      * @param int $phonenumber The phone number of the recipient in the format 254xxxxxxxxx
      * @param string $command_id The type of transaction being made. Can be SalaryPayment,BusinessPayment or PromotionPayment
      * @param string $remarks Any additional information. Must be present.
-     * @return object Curl Response from Mpesa
+     * @return \Illuminate\Http\Client\Response
      */
     public function b2c($phonenumber, $command_id, $amount, $remarks)
     {
@@ -196,8 +196,21 @@ public function b2c($phonenumber, $command_id, $amount, $remarks)
             "Occassion" => '', //can be null
         ];
 
-        $response = $this->MpesaRequest($url, $body);
-        return $response;
+        if (is_null($this->b2cresult)) {
+            throw CallbackException::make(
+                'b2c_result_url',
+                'Ensure you have set the B2C Result URL in the mpesa config file'
+            );
+        }
+
+        if (is_null($this->b2ctimeout)) {
+            throw CallbackException::make(
+                'b2c_timeout_url',
+                'Ensure you have set the B2C Timeout URL in the mpesa config file'
+            );
+        }
+
+        return $this->MpesaRequest($url, $body);
     }
     /**
      * Business to Client With Validation
@@ -220,7 +233,7 @@ public function b2c($phonenumber, $command_id, $amount, $remarks)
      * @param string $command_id The type of transaction being made. Can be SalaryPayment,BusinessPayment or PromotionPayment
      * @param string $remarks Any additional information. Must be present.
      * @param string $id_number The id number of the recipient
-     * @return object Curl Response from Mpesa
+     * @return \Illuminate\Http\Client\Response
      */
     public function validated_b2c($phonenumber, $command_id, $amount, $remarks, $id_number)
     {
@@ -240,6 +253,21 @@ public function validated_b2c($phonenumber, $command_id, $amount, $remarks, $id_
             "IDType" => "01", //01 for national id
             "IDNumber" => $id_number,
         ];
+
+        if (is_null($this->b2cresult)) {
+            throw CallbackException::make(
+                'b2c_result_url',
+                'Ensure you have set the B2C Result URL in the mpesa config file'
+            );
+        }
+
+        if (is_null($this->b2ctimeout)) {
+            throw CallbackException::make(
+                'b2c_timeout_url',
+                'Ensure you have set the B2C Timeout URL in the mpesa config file'
+            );
+        }
+
         return $this->MpesaRequest($url, $body);
     }
 
@@ -249,7 +277,7 @@ public function validated_b2c($phonenumber, $command_id, $amount, $remarks, $id_
      * This method is used to register URLs for callbacks when money is sent from the MPesa toolkit menu
      *
      * @param string $shortcode The till number or paybill number the urls will be associated with
-     * @return object Curl Response from Mpesa
+     * @return \Illuminate\Http\Client\Response 
      */
     public function c2bregisterURLS($shortcode)
     {
@@ -263,8 +291,21 @@ public function c2bregisterURLS($shortcode)
             "ValidationURL" => $this->c2bvalidate, //url should be https and should not contain keywords such as mpesa,safaricom etc
         ];
 
-        $response = $this->MpesaRequest($url, $body);
-        return $response;
+        if (is_null($this->c2bconfirm)) {
+            throw CallbackException::make(
+                'c2b_confirmation_url',
+                'Ensure you have set the C2B Confirmation URL in the mpesa config file'
+            );
+        }
+
+        if (is_null($this->c2bvalidate)) {
+            throw CallbackException::make(
+                'c2b_validation_url',
+                'Ensure you have set the C2B Validate URL in the mpesa config file'
+            );
+        }
+
+        return $this->MpesaRequest($url, $body);
     }
 
     /**
@@ -277,7 +318,7 @@ public function c2bregisterURLS($shortcode)
      * @param string $shortcode The Paybill/Till number receiving the funds
      * @param string $command_id The Type of transaction. Whether it is a paybill transaction(CustomerPayBillOnline) or a Till number transaction(CustomerBuyGoodsOnline)
      * @param string $account_number The account number for a paybill. The default is null
-     * @return object Curl Response from Safaricom
+     * @return \Illuminate\Http\Client\Response
      */
     public function c2bsimulate($phonenumber, $amount, $shortcode, $command_id, $account_number = null)
     {
@@ -303,9 +344,7 @@ public function c2bsimulate($phonenumber, $amount, $shortcode, $command_id, $acc
 
         $url = $this->url . '/mpesa/c2b/v2/simulate';
 
-
-        $response = $this->MpesaRequest($url, $data);
-        return $response;
+        return $this->MpesaRequest($url, $data);
     }
 
 
@@ -318,7 +357,7 @@ public function c2bsimulate($phonenumber, $amount, $shortcode, $command_id, $acc
      * @param string $transactionid Unique identifier to identify a transaction on M-Pesa
      * @param int $identiertype identifier to identify the orginization
      * @param string $remarks Any additional information. Must be present.
-     * @return object Curl Response from Safaricom
+     * @return \Illuminate\Http\Client\Response
      */
     public function transactionStatus($shortcode, $transactionid, $identiertype, $remarks)
     {
@@ -338,8 +377,21 @@ public function transactionStatus($shortcode, $transactionid, $identiertype, $re
             "Occassion" => "",
         ];
 
-        $response = $this->MpesaRequest($url, $body);
-        return $response;
+        if (is_null($this->statusresult)) {
+            throw CallbackException::make(
+                'status_result_url',
+                'Ensure you have set the Transaction Status Result URL in the mpesa config file'
+            );
+        }
+
+        if (is_null($this->statustimeout)) {
+            throw CallbackException::make(
+                'status_timeout_url',
+                'Ensure you have set the Transaction Status Timeout URL in the mpesa config file'
+            );
+        }
+
+        return $this->MpesaRequest($url, $body);
     }
 
     /**
@@ -350,7 +402,7 @@ public function transactionStatus($shortcode, $transactionid, $identiertype, $re
      * @param int $shortcode Organization/MSISDN receiving the transaction
      * @param int $identiertype identifier to identify the orginization
      * @param string $remarks Any additional information. Must be present.
-     * @return object Curl Response from Safaricom
+     * @return \Illuminate\Http\Client\Response
      */
     public function accountBalance($shortcode, $identiertype, $remarks)
     {
@@ -367,8 +419,21 @@ public function accountBalance($shortcode, $identiertype, $remarks)
             "QueueTimeOutURL" => $this->baltimeout,
         ];
 
-        $response = $this->MpesaRequest($url, $body);
-        return $response;
+        if (is_null($this->statusresult)) {
+            throw CallbackException::make(
+                'balance_result_url',
+                'Ensure you have set the Account Balance Result URL in the mpesa config file'
+            );
+        }
+
+        if (is_null($this->statustimeout)) {
+            throw CallbackException::make(
+                'balance_timeout_url',
+                'Ensure you have set the Account Balance Timeout URL in the mpesa config file'
+            );
+        }
+
+        return $this->MpesaRequest($url, $body);
     }
 
     /**
@@ -380,7 +445,7 @@ public function accountBalance($shortcode, $identiertype, $remarks)
      * @param int $shortcode Your Org's shortcode.
      * @param string $transactionid This is the M-Pesa Transaction ID of the transaction which you wish to reverse.
      * @param string $remarks Any additional information. Must be present.
-     * @return object Curl Response from Safaricom
+     * @return \Illuminate\Http\Client\Response
      */
     public function reversal($shortcode, $transactionid, $amount, $remarks)
     {
@@ -401,7 +466,20 @@ public function reversal($shortcode, $transactionid, $amount, $remarks)
             "Occasion" => ""
         ];
 
-        $response = $this->MpesaRequest($url, $body);
-        return $response;
+        if (is_null($this->reverseresult)) {
+            throw CallbackException::make(
+                'reversal_result_url',
+                'Ensure you have set the Reversal Result URL in the mpesa config file'
+            );
+        }
+
+        if (is_null($this->reversetimeout)) {
+            throw CallbackException::make(
+                'reversal_timeout_url',
+                'Ensure you have set the Reversal Timeout URL in the mpesa config file'
+            );
+        }
+
+        return $this->MpesaRequest($url, $body);
     }
 }
diff --git a/tests/TestCase.php b/tests/TestCase.php
index 50a40cd..1af48b4 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -2,7 +2,7 @@
 
 namespace Iankumu\Mpesa\Tests;
 
-use Iankumu\Mpesa\Mpesa;
+use Iankumu\Mpesa\MpesaServiceProvider;
 use Orchestra\Testbench\TestCase as Orchestra;
 
 class TestCase extends Orchestra
@@ -13,7 +13,6 @@ class TestCase extends Orchestra
     protected function setUp(): void
     {
         parent::setUp();
-        config(['app.url' => 'https://49cb48b01f608f.lhr.life']);
     }
 
     /*
@@ -27,6 +26,9 @@ protected function getEnvironmentSetUp($app)
     {
         // Alter the testing mpesa environment
         $app['config']->set('mpesa.environment', 'sandbox');
+        $app['config']->set('mpesa.mpesa_consumer_key', '12345');
+        $app['config']->set('mpesa.mpesa_consumer_secret', '12345');
+        $app['config']->set('mpesa.callback_url', null);
     }
 
     /**
@@ -35,7 +37,9 @@ protected function getEnvironmentSetUp($app)
      */
     protected function getPackageProviders($app)
     {
-        return ['Iankumu\Mpesa\MpesaServiceProvider'];
+        return [
+            MpesaServiceProvider::class
+        ];
     }
 
     /** @test */
diff --git a/tests/Unit/B2CTest.php b/tests/Unit/B2CTest.php
index a7abc49..b8a3437 100644
--- a/tests/Unit/B2CTest.php
+++ b/tests/Unit/B2CTest.php
@@ -4,6 +4,7 @@
 
 use Iankumu\Mpesa\Mpesa;
 use Iankumu\Mpesa\Tests\TestCase;
+use Iankumu\Mpesa\Exceptions\CallbackException;
 
 class B2CTest extends TestCase
 {
@@ -19,4 +20,13 @@ public function can_initiate_b2c()
         $result = $mpesa->b2c('0707070707', 'SalaryPayment', 100, 'Salary Payment');
         $this->assertSame(true, $result);
     }
+
+    /** @test */
+    public function b2c_will_throw_an_exception_when_the_callbacks_are_null()
+    {
+        $this->expectException(CallbackException::class);
+
+        //Should Throw an Exception as the callback is null
+        (new Mpesa())->b2c('0707070707', 'SalaryPayment', 100, 'Salary Payment');
+    }
 }
diff --git a/tests/Unit/C2BRegisterURLSTest.php b/tests/Unit/C2BRegisterURLSTest.php
index b3c656d..0192629 100644
--- a/tests/Unit/C2BRegisterURLSTest.php
+++ b/tests/Unit/C2BRegisterURLSTest.php
@@ -2,6 +2,7 @@
 
 namespace Iankumu\Mpesa\Tests\Unit;
 
+use Iankumu\Mpesa\Exceptions\CallbackException;
 use Iankumu\Mpesa\Mpesa;
 use Iankumu\Mpesa\Tests\TestCase;
 
@@ -18,4 +19,13 @@ public function can_register_c2b_urls()
 
         $this->assertSame(true, $mpesa->c2bregisterURLS(12345));
     }
+
+    /** @test */
+    public function c2b_will_throw_an_exception_when_the_callbacks_are_null()
+    {
+        $this->expectException(CallbackException::class);
+
+        //Should Throw an Exception as the callback is null
+        (new Mpesa())->c2bregisterURLS(12345);
+    }
 }
diff --git a/tests/Unit/GenerateSecurityCredentialTest.php b/tests/Unit/GenerateSecurityCredentialTest.php
index 33a2e56..835bb39 100644
--- a/tests/Unit/GenerateSecurityCredentialTest.php
+++ b/tests/Unit/GenerateSecurityCredentialTest.php
@@ -4,7 +4,6 @@
 
 use Iankumu\Mpesa\Mpesa;
 use Iankumu\Mpesa\Tests\TestCase;
-use Iankumu\Mpesa\Utils\MpesaHelper;
 
 class GenerateSecurityCredentialTest extends TestCase
 {
diff --git a/tests/Unit/MpesaSTKTest.php b/tests/Unit/MpesaSTKTest.php
index d26abae..179fad5 100644
--- a/tests/Unit/MpesaSTKTest.php
+++ b/tests/Unit/MpesaSTKTest.php
@@ -2,6 +2,7 @@
 
 namespace Iankumu\Mpesa\Tests\Unit;
 
+use Iankumu\Mpesa\Exceptions\CallbackException;
 use Iankumu\Mpesa\Mpesa;
 use Iankumu\Mpesa\Tests\TestCase;
 
@@ -18,4 +19,13 @@ public function can_initiate_stkpush()
 
         $this->assertSame(true, $result);
     }
+
+    /** @test */
+    public function stkpush_will_throw_an_exception_when_the_callbacks_are_null()
+    {
+        $this->expectException(CallbackException::class);
+
+        //Should Throw an Exception as the callback is null
+        (new Mpesa())->stkpush('0707070707', 100, 12345);
+    }
 }
diff --git a/tests/Unit/ValidatedB2CTest.php b/tests/Unit/ValidatedB2CTest.php
index cb298e0..bd6a465 100644
--- a/tests/Unit/ValidatedB2CTest.php
+++ b/tests/Unit/ValidatedB2CTest.php
@@ -2,6 +2,7 @@
 
 namespace Iankumu\Mpesa\Tests\Unit;
 
+use Iankumu\Mpesa\Exceptions\CallbackException;
 use Iankumu\Mpesa\Mpesa;
 use Iankumu\Mpesa\Tests\TestCase;
 use Illuminate\Support\Facades\Log;
@@ -15,10 +16,10 @@ public function can_validate_b2c()
         $mpesa = $this->createStub(Mpesa::class);
 
         $mpesa->method('validated_b2c')
-            ->with('0707070707', 'SalaryPayment', 100, 'Salary Payment','120912992')//Will take a phone number and ID Number of the person to be paid
+            ->with('0707070707', 'SalaryPayment', 100, 'Salary Payment', '120912992') //Will take a phone number and ID Number of the person to be paid
             ->willReturn(true);
 
-        $result = $mpesa->validated_b2c('0707070707', 'SalaryPayment', 100, 'Salary Payment','120912992');
+        $result = $mpesa->validated_b2c('0707070707', 'SalaryPayment', 100, 'Salary Payment', '120912992');
         $result->assertJsonStructure([
             'ConversationID',
             'OriginatorConversationID',
@@ -26,4 +27,13 @@ public function can_validate_b2c()
             'ResponseDescription',
         ]);
     }
+
+    /** @test */
+    public function validated_b2c_will_throw_an_exception_when_the_callbacks_are_null()
+    {
+        $this->expectException(CallbackException::class);
+
+        //Should Throw an Exception as the callback is null
+        (new Mpesa())->validated_b2c('0707070707', 'SalaryPayment', 100, 'Salary Payment', '120912992');;
+    }
 }