diff --git a/modules/sms_track/sms_track.module b/modules/sms_track/sms_track.module
index f4e3bec..6afe938 100644
--- a/modules/sms_track/sms_track.module
+++ b/modules/sms_track/sms_track.module
@@ -63,10 +63,10 @@ function sms_track_sms_send(SmsMessageInterface $sms, array $options, GatewayInt
  *   Additional options array including sender.
  * @param \Drupal\sms\Gateway\GatewayInterface $gateway
  *   Gateway array for the active gateway.
- * @param array $result
- *   Result array from the gateway response handler.
+ * @param bool|array $result
+ *   The result from the gateway response handler.
  */
-function sms_track_sms_send_process($op, SmsMessageInterface $sms, array $options, GatewayInterface $gateway, array $result) {
+function sms_track_sms_send_process($op, SmsMessageInterface $sms, array $options, GatewayInterface $gateway, $result) {
   if ($op == 'post process') {
     // Archiving (outgoing == 0)
     $dir = 0;
diff --git a/src/Gateway/GatewayBase.php b/src/Gateway/GatewayBase.php
index 75b8cce..428caa6 100644
--- a/src/Gateway/GatewayBase.php
+++ b/src/Gateway/GatewayBase.php
@@ -9,7 +9,7 @@ namespace Drupal\sms\Gateway;
 
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Plugin\PluginBase;
-use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Symfony\Component\HttpFoundation\Request;
 
 /**
  * Base class for sms gateway plugins.
@@ -168,6 +168,27 @@ abstract class GatewayBase extends PluginBase implements GatewayInterface {
   }
 
   /**
+   * {@inheritdoc}
+   */
+  public function balance() {
+    return 0;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function deliveryReport(Request $request) {
+    return;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getError() {
+    return array();
+  }
+
+  /**
    * Gets the Psr logger for this gateway.
    */
   protected function logger() {
diff --git a/src/Gateway/GatewayInterface.php b/src/Gateway/GatewayInterface.php
index 9d3aea8..48f0f85 100644
--- a/src/Gateway/GatewayInterface.php
+++ b/src/Gateway/GatewayInterface.php
@@ -18,9 +18,6 @@ use Symfony\Component\HttpFoundation\Request;
  */
 interface GatewayInterface extends ConfigurablePluginInterface, PluginFormInterface {
 
-  // Gateway response codes
-  // 0=Unknown, 2xx=Positive, 4xx=Negative(likely client err), 5xx=Negative(likely gateway err)
-
   /**
    * Status Unknown.
    *
@@ -114,15 +111,6 @@ interface GatewayInterface extends ConfigurablePluginInterface, PluginFormInterf
   const STATUS_ERR_OTHER = 500;
 
   /**
-   * Use get
-   * Connection methods
-   */
-  const HTTP_GET_SPLIT = 0;
-  const HTTP_GET = 1;
-  const HTTP_POST = 2;
-  const SMPP = 3;
-
-  /**
    * Sends an sms and invokes the corresponding sms receipt method.
    *
    * @param \Drupal\sms\Message\SmsMessageInterface $sms
diff --git a/src/Gateway/GatewayManager.php b/src/Gateway/GatewayManager.php
index 105b633..63ea7ee 100644
--- a/src/Gateway/GatewayManager.php
+++ b/src/Gateway/GatewayManager.php
@@ -196,9 +196,7 @@ class GatewayManager extends DefaultPluginManager implements GatewayManagerInter
     foreach ($instance_configs as $id => $instance_config) {
       // Note that DefaultFactory::createInstance will get the right definitions.
       if (!isset($instance_config['plugin_id'])) {
-        // @todo Throw exception here???
-//        throw new \InvalidArgumentException(sprintf('Gateway %s configured without a plugin id.', $id));
-        continue;
+        throw new \InvalidArgumentException(sprintf('Gateway %s configured without a plugin id.', $id));
       }
       $this->gateways[$id] = $this->createInstance($instance_config['plugin_id'], $instance_config);
       $this->names[$id] = $this->gateways[$id]->getLabel();
diff --git a/src/Gateway/HookGateway.php b/src/Gateway/HookGateway.php
index a57092c..9c7c134 100644
--- a/src/Gateway/HookGateway.php
+++ b/src/Gateway/HookGateway.php
@@ -46,6 +46,9 @@ class HookGateway extends GatewayBase {
    * {@inheritdoc}
    */
   public function balance() {
+    if (is_callable($this->pluginDefinition['balance'])) {
+      return $this->pluginDefinition['balance']();
+    }
     return 0;
   }
 
@@ -53,14 +56,9 @@ class HookGateway extends GatewayBase {
    * {@inheritdoc}
    */
   public function deliveryReport(Request $request) {
-    return;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function getError() {
-    return array();
+    if (is_callable($this->pluginDefinition['delivery report'])) {
+      return $this->pluginDefinition['delivery report']();
+    }
   }
 
   /**
diff --git a/src/Plugin/Gateway/LogGateway.php b/src/Plugin/Gateway/LogGateway.php
index 4e5c08d..59e0a2a 100644
--- a/src/Plugin/Gateway/LogGateway.php
+++ b/src/Plugin/Gateway/LogGateway.php
@@ -9,7 +9,6 @@ namespace Drupal\sms\Plugin\Gateway;
 use Drupal\sms\Gateway\GatewayBase;
 use Drupal\sms\Message\SmsMessageInterface;
 use Drupal\sms\Message\SmsMessageResult;
-use Symfony\Component\HttpFoundation\Request;
 
 /**
  * @SmsGateway(
@@ -22,35 +21,12 @@ class LogGateway extends GatewayBase {
 
   /**
    * {@inheritdoc}
-   *
-   * Log sms message to drupal watchdog().
    */
   public function send(SmsMessageInterface $sms, array $options) {
+    // Log sms message to drupal logger.
     $this->logger()->notice('SMS message sent to %number with the text: @message',
       ['%number' => implode(', ', $sms->getRecipients()), '@message' => $sms->getMessage()]);
     return new SmsMessageResult(['status' => TRUE]);
   }
 
-
-  /**
-   * {@inheritdoc}
-   */
-  public function balance() {
-    return 0;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function deliveryReport(Request $request) {
-    return;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function getError() {
-    return array();
-  }
-
 }
diff --git a/src/Provider/DefaultSmsProvider.php b/src/Provider/DefaultSmsProvider.php
index 7e37752..712cac0 100644
--- a/src/Provider/DefaultSmsProvider.php
+++ b/src/Provider/DefaultSmsProvider.php
@@ -121,10 +121,10 @@ class DefaultSmsProvider implements SmsProviderInterface {
    *   Additional options that were passed to the SMS gateway.
    * @param \Drupal\sms\Gateway\GatewayInterface $gateway
    *   The default gateway for sending this message.
-   * @param array $result
-   *   The result returned from SMS sending.
+   * @param bool|array $result
+   *   The result from the gateway response handler.
    */
-  protected function postProcess(SmsMessageInterface $sms, array $options, GatewayInterface $gateway, array $result) {
+  protected function postProcess(SmsMessageInterface $sms, array $options, GatewayInterface $gateway, $result) {
     // Call the send post process hooks.
     $this->moduleHandler->invokeAll('sms_send_process', ['post process', $sms, $options, $gateway, $result]);
   }