diff --git a/src/Message/AbstractRequest.php b/src/Message/AbstractRequest.php
index 72b9e10..8e9bbff 100644
--- a/src/Message/AbstractRequest.php
+++ b/src/Message/AbstractRequest.php
@@ -39,7 +39,7 @@ public function setSecureHash($value)
     {
         return $this->setParameter('secureHash', $value);
     }
-    
+
     public function getLocaleCode()
     {
         return $this->getParameter('localeCode');
@@ -50,18 +50,51 @@ public function setLocaleCode($value)
         return $this->setParameter('localeCode', $value);
     }
 
+    public function getTransactionNo()
+    {
+        return $this->getParameter('transactionNo');
+    }
+
+    public function setTransactionNo($value)
+    {
+        return $this->setParameter('transactionNo', $value);
+    }
+
+    public function getUser()
+    {
+        return $this->getParameter('user');
+    }
+
+    public function setUser($value)
+    {
+        return $this->setParameter('user', $value);
+    }
+
+    public function getPassword()
+    {
+        return $this->getParameter('password');
+    }
+
+    public function setPassword($value)
+    {
+        return $this->setParameter('password', $value);
+    }
+
     protected function getBaseData()
     {
         $data = array();
         $data['vpc_Merchant']   = $this->getMerchantId();
         $data['vpc_AccessCode'] = $this->getMerchantAccessCode();
         $data['vpc_Version']    = '1';
-        $data['vpc_Locale']     = $this->getLocaleCode();
         $data['vpc_Command']    = $this->action;
         $data['vpc_Amount']      = $this->getAmountInteger();
         $data['vpc_MerchTxnRef'] = $this->getTransactionId();
-        $data['vpc_OrderInfo']   = $this->getDescription();
-        $data['vpc_ReturnURL']   = $this->getReturnUrl();
+        
+        if ($this->action != 'refund') {
+            $data['vpc_Locale']      = $this->getLocaleCode() != null ? $this->getLocaleCode() : 'en';
+            $data['vpc_OrderInfo']   = $this->getDescription();
+            $data['vpc_ReturnURL']   = $this->getReturnUrl();
+        }
 
         return $data;
     }
diff --git a/src/Message/Response.php b/src/Message/Response.php
index 10431f7..bde9c0f 100644
--- a/src/Message/Response.php
+++ b/src/Message/Response.php
@@ -21,7 +21,7 @@ public function __construct(RequestInterface $request, $data)
 
     public function isSuccessful()
     {
-        return isset($this->data['vpc_TxnResponseCode']) && "0" === $this->data['vpc_TxnResponseCode'];
+        return "0" === $this->getCode();
     }
 
     public function getTransactionReference()
@@ -33,4 +33,9 @@ public function getMessage()
     {
         return isset($this->data['vpc_Message']) ? $this->data['vpc_Message'] : null;
     }
+    
+    public function getCode()
+    {
+        return isset($this->data['vpc_TxnResponseCode']) ? $this->data['vpc_TxnResponseCode'] : null;
+    }
 }
diff --git a/src/Message/ThreePartyRefundRequest.php b/src/Message/ThreePartyRefundRequest.php
index b724e76..e183d55 100644
--- a/src/Message/ThreePartyRefundRequest.php
+++ b/src/Message/ThreePartyRefundRequest.php
@@ -2,8 +2,6 @@
 
 namespace Omnipay\Migs\Message;
 
-use Omnipay\Common\Exception\InvalidRequestException;
-
 /**
  * Migs Complete Purchase Request
  */
@@ -12,10 +10,10 @@ class ThreePartyRefundRequest extends AbstractRequest
     protected $action = 'refund';
     public function getData()
     {
-        $this->validate('amount', 'returnUrl', 'transactionId');
+        $this->validate('amount', 'transactionId', 'user', 'password');
         $data = $this->getBaseData();
         $data['vpc_SecureHash']  = $this->calculateHash($data);
-        $data['vpc_TransNo'] = $this->getParameter('transactionNo');
+        $data['vpc_TransNo'] = $this->getTransactionNo();
         $data['vpc_User']  = $this->getUser();
         $data['vpc_Password']  = $this->getPassword();
         return $data;
diff --git a/tests/Message/ThreePartyCompletePurchaseRequestTest.php b/tests/Message/ThreePartyCompletePurchaseRequestTest.php
index 79ea430..3fef90d 100644
--- a/tests/Message/ThreePartyCompletePurchaseRequestTest.php
+++ b/tests/Message/ThreePartyCompletePurchaseRequestTest.php
@@ -27,7 +27,7 @@ public function testThreePartyCompletePurchaseSuccess()
         $this->assertFalse($response->isRedirect());
         $this->assertSame('12345', $response->getTransactionReference());
         $this->assertSame('Approved', $response->getMessage());
-        $this->assertNull($response->getCode());
+        $this->assertSame('0', $response->getCode());
     }
 
     public function testThreePartyCompletePurchaseFailure()
@@ -46,6 +46,6 @@ public function testThreePartyCompletePurchaseFailure()
         $this->assertFalse($response->isRedirect());
         $this->assertSame('12345', $response->getTransactionReference());
         $this->assertNotSame('Approved', $response->getMessage());
-        $this->assertNull($response->getCode());
+        $this->assertSame('1', $response->getCode());
     }
 }
diff --git a/tests/Message/ThreePartyRefundRequestTest.php b/tests/Message/ThreePartyRefundRequestTest.php
index e69de29..77dee61 100644
--- a/tests/Message/ThreePartyRefundRequestTest.php
+++ b/tests/Message/ThreePartyRefundRequestTest.php
@@ -0,0 +1,68 @@
+<?php
+
+namespace Omnipay\Migs\Message;
+
+use Omnipay\Tests\TestCase;
+
+class ThreePartyRefundRequestTest extends TestCase
+{
+    public function setUp()
+    {
+        $this->request = new ThreePartyRefundRequest($this->getHttpClient(), $this->getHttpRequest());
+    }
+
+    public function testSignature()
+    {
+        $this->request->initialize(
+            array(
+                'amount'             => '12.00',
+                'transactionId'      => 123,
+
+                'merchantId'         => '123',
+                'merchantAccessCode' => '123',
+                'secureHash'         => '123',
+
+                'transactionNo' => '1112',
+
+                'user' => 'amauser',
+                'password' => 'amapassword'
+            )
+        );
+
+        $data = $this->request->getData();
+
+        $this->assertSame('80E8AD6C582431F9C8A55C9645EE2F05BA70D178EB0A85E7394331DC09B61875', $data['vpc_SecureHash']);
+    }
+
+    /**
+     * @depends testSignature
+     */
+    public function testRefund()
+    {
+        $this->request->initialize(
+            array(
+                'amount'             => '12.00',
+                'transactionId'      => 123,
+
+                'merchantId'         => '123',
+                'merchantAccessCode' => '123',
+                'secureHash'         => '123',
+                
+                'transactionNo' => '1112',
+
+                'user' => 'amauser',
+                'password' => 'amapassword'
+            )
+        );
+        
+        $response = $this->request->send();
+        $this->assertInstanceOf('Omnipay\Migs\Message\Response', $response);
+        $this->assertFalse($response->isSuccessful());
+        $this->assertFalse($response->isRedirect());
+        $this->assertSame('7', $response->getCode());
+        $this->assertSame(
+            'E5000: Merchant [123] does not have the required privilege to use the VirtualPaymentClient API.',
+            $response->getMessage()
+        );
+    }
+}
diff --git a/tests/Message/TwoPartyPurchaseRequestTest.php b/tests/Message/TwoPartyPurchaseRequestTest.php
index 467702a..fbd8b14 100644
--- a/tests/Message/TwoPartyPurchaseRequestTest.php
+++ b/tests/Message/TwoPartyPurchaseRequestTest.php
@@ -58,7 +58,7 @@ public function testPurchase()
         $this->assertFalse($response->isRedirect());
         $this->assertEquals('12345', $response->getTransactionReference());
         $this->assertSame('Approved', $response->getMessage());
-        $this->assertNull($response->getCode());
+        $this->assertSame('0', $response->getCode());
         $this->assertArrayHasKey('vpc_SecureHash', $response->getData());
     }
 }
diff --git a/tests/Message/TwoPartyPurchaseResponseTest.php b/tests/Message/TwoPartyPurchaseResponseTest.php
index 54b4529..8438591 100644
--- a/tests/Message/TwoPartyPurchaseResponseTest.php
+++ b/tests/Message/TwoPartyPurchaseResponseTest.php
@@ -16,7 +16,7 @@ public function testTwoPartyPurchaseSuccess()
         $this->assertFalse($response->isRedirect());
         $this->assertSame('12345', $response->getTransactionReference());
         $this->assertSame('Approved', $response->getMessage());
-        $this->assertNull($response->getCode());
+        $this->assertSame('0', $response->getCode());
     }
 
     public function testTwoPartyPurchaseFailure()
@@ -29,6 +29,6 @@ public function testTwoPartyPurchaseFailure()
         $this->assertFalse($response->isRedirect());
         $this->assertSame('12345', $response->getTransactionReference());
         $this->assertSame('Declined', $response->getMessage());
-        $this->assertNull($response->getCode());
+        $this->assertSame('2', $response->getCode());
     }
 }
diff --git a/tests/ThreePartyGatewayTest.php b/tests/ThreePartyGatewayTest.php
index 4e8c847..03d10a8 100644
--- a/tests/ThreePartyGatewayTest.php
+++ b/tests/ThreePartyGatewayTest.php
@@ -39,11 +39,21 @@ public function testCompletePurchase()
 
     public function testRefund()
     {
-        $request = $this->gateway->refund(array('amount' => '10.00', 'transactionNo' => '1112'));
+        $request = $this->gateway->refund(array(
+            'amount' => '10.00',
+            'transactionNo' => '1112',
+            'user' => 'amauser',
+            'password' =>'amapassword'
+        ));
 
         $this->assertInstanceOf('\Omnipay\Migs\Message\ThreePartyRefundRequest', $request);
 
         $this->assertSame('10.00', $request->getAmount());
-    }
 
+        $this->assertSame('1112', $request->getTransactionNo());
+
+        $this->assertSame('amauser', $request->getUser());
+
+        $this->assertSame('amapassword', $request->getPassword());
+    }
 }