I wish this help you After talking to the customer support of Clickatell, i figured out that there are two places to add callback urls inside your clickatell account. The first one is under the API which i was adding and it wasn't working. The second, and correct place for my case, was under the mobile number settings. To be completely clear, if you check under the SB Subscriptions link in your account, you would see a mobile number and a settings link next to it. That is where you need to add the callback url. everyone for your responses.