diff --git a/src/TransportInterface.php b/src/TransportInterface.php
index <HASH>..<HASH> 100644
--- a/src/TransportInterface.php
+++ b/src/TransportInterface.php
@@ -89,11 +89,11 @@ interface TransportInterface
     /**
      * API call for "getMsgCharge".
      *
-     * @param string $apiMsgId ApiMsgId to query
+     * @param string $msgId ApiMsgId to query
      *
-     * @throws Exception
+     * @param bool   $cliMsgId is this a client MsgId?
      *
      * @return mixed
      */
-    public function getMessageCharge($apiMsgId);
+    public function getMessageCharge($msgId, $cliMsgId = false);
 }
\ No newline at end of file
Update Interface to allow for cliMsgId