diff --git a/src/Message/ChargeRequest.php b/src/Message/ChargeRequest.php
index 6efcd74..d7772e2 100755
--- a/src/Message/ChargeRequest.php
+++ b/src/Message/ChargeRequest.php
@@ -182,7 +182,7 @@ public function sendData($data)
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when creating transaction: ', $e->getMessage()
+                'detail' => 'Exception when creating transaction: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/ChargeResponse.php b/src/Message/ChargeResponse.php
index 147805e..8d2f14d 100755
--- a/src/Message/ChargeResponse.php
+++ b/src/Message/ChargeResponse.php
@@ -38,27 +38,27 @@ public function getRedirectData()
 
     public function getTransactionId()
     {
-        return $this->data['transactionId'];
+        return $this->data['transactionId'] ?? null;
     }
 
     public function getTenders()
     {
-        return $this->data['tenders'];
+        return $this->data['tenders'] ?? null;
     }
 
     public function getOrderId()
     {
-        return $this->data['orderId'];
+        return $this->data['orderId'] ?? null;
     }
 
     public function getCreatedAt()
     {
-        return $this->data['created_at'];
+        return $this->data['created_at'] ?? null;
     }
 
     public function getReferenceId()
     {
-        return $this->data['referenceId'];
+        return $this->data['referenceId'] ?? null;
     }
 
     public function getMessage()
@@ -68,7 +68,7 @@ public function getMessage()
             $message .= $this->data['code'] . ': ';
         }
 
-        return $message . ($this->data['error'] ?? '');
+        return $message . ($this->data['detail'] ?? '');
     }
 
     /**
@@ -84,10 +84,10 @@ public function getTransactionReference()
     /**
      * Get the tender id that is used for processing refunds
      *
-     * @return string
+     * @return null|string
      */
     public function getBillingId()
     {
-        return $this->getTenders()[0]['id'];
+        return $this->getTenders()[0]['id'] ?? null;
     }
 }
diff --git a/src/Message/CreateCardRequest.php b/src/Message/CreateCardRequest.php
index cef51bf..12d577b 100644
--- a/src/Message/CreateCardRequest.php
+++ b/src/Message/CreateCardRequest.php
@@ -86,7 +86,7 @@ public function sendData($data)
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when creating card: ', $e->getMessage()
+                'detail' => 'Exception when creating card: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/CreateCustomerRequest.php b/src/Message/CreateCustomerRequest.php
index 596e1d1..a309c75 100644
--- a/src/Message/CreateCustomerRequest.php
+++ b/src/Message/CreateCustomerRequest.php
@@ -60,6 +60,16 @@ public function setEmail($value)
         return $this->setParameter('email', $value);
     }
 
+    public function getReferenceId()
+    {
+        return $this->getParameter('referenceId');
+    }
+
+    public function setReferenceId($value)
+    {
+        return $this->setParameter('referenceId', $value);
+    }
+
     public function getData()
     {
         $data = [];
@@ -68,6 +78,7 @@ public function getData()
         $data['family_name'] = $this->getLastName();
         $data['company_name'] = $this->getCompanyName();
         $data['email_address'] = $this->getEmail();
+        $data['reference_id'] = $this->getReferenceId();
 
         return $data;
     }
@@ -96,7 +107,7 @@ public function sendData($data)
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when creating customer: ', $e->getMessage()
+                'detail' => 'Exception when creating customer: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/DeleteCardRequest.php b/src/Message/DeleteCardRequest.php
index 9afabe7..af14f73 100644
--- a/src/Message/DeleteCardRequest.php
+++ b/src/Message/DeleteCardRequest.php
@@ -91,7 +91,7 @@ public function sendData($data)
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when creating card: ', $e->getMessage()
+                'detail' => 'Exception when creating card: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/DeleteCustomerRequest.php b/src/Message/DeleteCustomerRequest.php
index 30fbbda..a76ddc2 100644
--- a/src/Message/DeleteCustomerRequest.php
+++ b/src/Message/DeleteCustomerRequest.php
@@ -78,7 +78,7 @@ public function sendData($data)
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when creating customer: ', $e->getMessage()
+                'detail' => 'Exception when creating customer: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/FetchCardRequest.php b/src/Message/FetchCardRequest.php
index 64bae60..f829b29 100644
--- a/src/Message/FetchCardRequest.php
+++ b/src/Message/FetchCardRequest.php
@@ -97,7 +97,7 @@ public function sendData($data)
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when creating customer: ', $e->getMessage()
+                'detail' => 'Exception when creating customer: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/FetchCustomerRequest.php b/src/Message/FetchCustomerRequest.php
index 29a6385..3e450a0 100644
--- a/src/Message/FetchCustomerRequest.php
+++ b/src/Message/FetchCustomerRequest.php
@@ -83,7 +83,7 @@ public function sendData($data)
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when creating customer: ', $e->getMessage()
+                'detail' => 'Exception when creating customer: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/ListRefundsRequest.php b/src/Message/ListRefundsRequest.php
index 1a689cc..62d11ca 100644
--- a/src/Message/ListRefundsRequest.php
+++ b/src/Message/ListRefundsRequest.php
@@ -137,7 +137,7 @@ public function sendData()
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when calling TransactionsApi->listRefunds: ', $e->getMessage()
+                'detail' => 'Exception when calling TransactionsApi->listRefunds: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/ListTransactionsRequest.php b/src/Message/ListTransactionsRequest.php
index 16d07d6..e6823fd 100644
--- a/src/Message/ListTransactionsRequest.php
+++ b/src/Message/ListTransactionsRequest.php
@@ -187,7 +187,7 @@ public function sendData()
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when calling TransactionsApi->listTransactions: ', $e->getMessage()
+                'detail' => 'Exception when calling TransactionsApi->listTransactions: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/RefundRequest.php b/src/Message/RefundRequest.php
index b43dd5d..abf0d9a 100755
--- a/src/Message/RefundRequest.php
+++ b/src/Message/RefundRequest.php
@@ -123,7 +123,7 @@ public function sendData($data)
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when creating refund: ', $e->getMessage()
+                'detail' => 'Exception when creating refund: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/TransactionRequest.php b/src/Message/TransactionRequest.php
index 81caa2d..4045acd 100644
--- a/src/Message/TransactionRequest.php
+++ b/src/Message/TransactionRequest.php
@@ -100,7 +100,7 @@ public function sendData($data)
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when calling LocationsApi->listLocations: ', $e->getMessage()
+                'detail' => 'Exception when calling LocationsApi->listLocations: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/UpdateCustomerRequest.php b/src/Message/UpdateCustomerRequest.php
index 162f7c6..766f58e 100644
--- a/src/Message/UpdateCustomerRequest.php
+++ b/src/Message/UpdateCustomerRequest.php
@@ -179,7 +179,7 @@ public function sendData($data)
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when creating customer: ', $e->getMessage()
+                'detail' => 'Exception when creating customer: ' . $e->getMessage()
             ];
         }
 
diff --git a/src/Message/WebPaymentRequest.php b/src/Message/WebPaymentRequest.php
index 6dc1f02..32fbf09 100644
--- a/src/Message/WebPaymentRequest.php
+++ b/src/Message/WebPaymentRequest.php
@@ -84,7 +84,7 @@ public function sendData($data)
         } catch (\Exception $e) {
             $response = [
                 'status' => 'error',
-                'detail' => 'Exception when creating web payment request: ', $e->getMessage()
+                'detail' => 'Exception when creating web payment request: ' . $e->getMessage()
             ];
         }