diff --git a/src/Contract/PaymentMethod/CreditCard.php b/src/Contract/PaymentMethod/CreditCard.php
index cb99bc2..9df509d 100644
--- a/src/Contract/PaymentMethod/CreditCard.php
+++ b/src/Contract/PaymentMethod/CreditCard.php
@@ -6,7 +6,7 @@
 use Nekoding\LaravelSoftbank\Contract\PaymentService;
 use Nekoding\LaravelSoftbank\Contract\Response;
 
-interface CreditCard extends PaymentService
+abstract class CreditCard extends PaymentService
 {
     
     /**
@@ -15,7 +15,7 @@ interface CreditCard extends PaymentService
      * @param  \Nekoding\LaravelSoftbank\Contract\Payload $payload
      * @return Response
      */
-    public function partialRefundTransaction(Payload $payload): Response;
+    public abstract function partialRefundTransaction(Payload $payload): Response;
     
     /**
      * saveCard
@@ -23,6 +23,6 @@ public function partialRefundTransaction(Payload $payload): Response;
      * @param  \Nekoding\LaravelSoftbank\Contract\Payload $payload
      * @return Response
      */
-    public function saveCard(Payload $payload): Response;
+    public abstract function saveCard(Payload $payload): Response;
 
 }
\ No newline at end of file
diff --git a/src/Contract/PaymentService.php b/src/Contract/PaymentService.php
index 20854b2..04f2e2b 100644
--- a/src/Contract/PaymentService.php
+++ b/src/Contract/PaymentService.php
@@ -2,10 +2,37 @@
 
 namespace Nekoding\LaravelSoftbank\Contract;
 
-interface PaymentService
+use Nekoding\LaravelSoftbank\Contract\Payload;
+use Nekoding\LaravelSoftbank\PaymentMethod\SoftbankResponse;
+use Nekoding\LaravelSoftbank\Traits\HttpClient\SoftbankHttpClient;
+use Nekoding\LaravelSoftbank\Traits\Payload\PayloadSerializer;
+
+abstract class PaymentService
 {
 
-    public function createRequest(Payload $payload, string $requestId): Response;
+    use PayloadSerializer;
+    use SoftbankHttpClient;
+    
+    /**
+     * createRequest
+     *
+     * @param   \Nekoding\LaravelSoftbank\Contract\Payload $payload
+     * @param  string $requestId
+     * @return Response
+     */
+    public function createRequest(Payload $payload, string $requestId): Response
+    {
+        $body = $this->generatePayload($payload, $requestId);
+
+        $response = $this->postData($body, ['username' => $payload->getAuthUsername(), 'password' => $payload->getAuthPassword()]);
+
+        /**
+         * @var \Nekoding\LaravelSoftbank\PaymentMethod\SoftbankResponse
+         */
+        $result = $this->deserializeData($response->body(), SoftbankResponse::class);
+
+        return $result;
+    }
 
     /**
      * createTransaction
@@ -13,7 +40,7 @@ public function createRequest(Payload $payload, string $requestId): Response;
      * @param  \Nekoding\LaravelSoftbank\Contract\Payload $payload
      * @return Response
      */
-    public function createTransaction(Payload $payload): Response;
+    public abstract function createTransaction(Payload $payload): Response;
 
     
     /**
@@ -22,7 +49,7 @@ public function createTransaction(Payload $payload): Response;
      * @param  \Nekoding\LaravelSoftbank\Contract\Payload $payload
      * @return Response
      */
-    public function confirmTransaction(Payload $payload): Response;
+    public abstract function confirmTransaction(Payload $payload): Response;
 
         
     /**
@@ -31,7 +58,7 @@ public function confirmTransaction(Payload $payload): Response;
      * @param  \Nekoding\LaravelSoftbank\Contract\Payload $payload
      * @return Response
      */
-    public function marksTransactionSales(Payload $payload): Response;
+    public abstract function marksTransactionSales(Payload $payload): Response;
     
     /**
      * refundTransaction
@@ -39,5 +66,5 @@ public function marksTransactionSales(Payload $payload): Response;
      * @param  \Nekoding\LaravelSoftbank\Contract\Payload $payload
      * @return Response
      */
-    public function refundTransaction(Payload $payload): Response;
+    public abstract function refundTransaction(Payload $payload): Response;
 }
diff --git a/src/PaymentMethod/CreditCard/CreditCardPayment.php b/src/PaymentMethod/CreditCard/CreditCardPayment.php
index b422559..081f263 100644
--- a/src/PaymentMethod/CreditCard/CreditCardPayment.php
+++ b/src/PaymentMethod/CreditCard/CreditCardPayment.php
@@ -5,18 +5,9 @@
 use Nekoding\LaravelSoftbank\Contract\Payload;
 use Nekoding\LaravelSoftbank\Contract\PaymentMethod\CreditCard;
 use Nekoding\LaravelSoftbank\Contract\Response;
-use Nekoding\LaravelSoftbank\PaymentMethod\SoftbankResponse;
-use Nekoding\LaravelSoftbank\Traits\HttpClient\SoftbankHttpClient;
-use Nekoding\LaravelSoftbank\Traits\Payload\CanChangeRequestId;
-use Nekoding\LaravelSoftbank\Traits\Payload\PayloadSerializer;
 
-class CreditCardPayment implements CreditCard
+class CreditCardPayment extends CreditCard
 {
-
-    use PayloadSerializer;
-    use SoftbankHttpClient;
-    use CanChangeRequestId;
-
     protected $paymentRequestId         = 'ST01-00101-101';
     protected $confirmationRequestId    = 'ST02-00101-101';
     protected $salesRequestId           = 'ST02-00201-101';
@@ -33,20 +24,6 @@ class CreditCardPayment implements CreditCard
     protected $getCardInfoRequestId     = '';
 
 
-    public function createRequest(Payload $payload, string $requestId): Response
-    {
-        $body = $this->generatePayload($payload, $requestId);
-
-        $response = $this->postData($body, ['username' => $payload->getAuthUsername(), 'password' => $payload->getAuthPassword()]);
-
-        /**
-         * @var \Nekoding\LaravelSoftbank\PaymentMethod\SoftbankResponse
-         */
-        $result = $this->deserializeData($response->body(), SoftbankResponse::class);
-
-        return $result;
-    }
-
     public function createTransaction(Payload $payload): Response
     {
         return $this->createRequest($payload, $this->paymentRequestId);
diff --git a/src/Traits/Payload/CanChangeRequestId.php b/src/Traits/Payload/CanChangeRequestId.php
deleted file mode 100644
index 43a7727..0000000
--- a/src/Traits/Payload/CanChangeRequestId.php
+++ /dev/null
@@ -1,17 +0,0 @@
-<?php
-
-namespace Nekoding\LaravelSoftbank\Traits\Payload;
-
-trait CanChangeRequestId
-{
-
-    protected $requestId;
-
-    public function setRequestId(string $requestId): self
-    {
-        $this->requestId = $requestId;
-
-        return $this;
-    }
-
-}
\ No newline at end of file