Having problems setting up sms api

I am having problems setting up SMS gateway. I have entered the settings as per the API give, but I am not receiving any message, nor am i getting any error, Just getting a message that sms sent. However sending from the browser directly sends the message.

any suggestions?

http://www.smsjust.com /sms/user/urlsms.php?username=XXXX&pass=XXXX&senderid=XXXX&dest_mobileno=XXXX&message=XXXX&response=Y