in sms gate way error occures error is | 106 | The method "SENDMESSAGE" is not supported.

string stru = "http://enterprise.smsgupshup.com/GatewayAPI/rest?method=SendMessage&send_to=9747447228&msg=Welcome&msg_type=TEXT&userid=xxxxxxx&auth_scheme=plain&password=xxxxxxx&v=1.1&format=text";
           // Create a request object
           WebRequest request = HttpWebRequest.Create(stru);
           // Get the response back
           HttpWebResponse response = (HttpWebResponse)request.GetResponse();
           sm = (Stream)response.GetResponseStream();
           StreamReader readStream = new StreamReader(sm);
           string dataString = readStream.ReadToEnd();
           response.Close();
           sm.Close();
           readStream.Close();