Does iMessage require SMS to activate? I am overseas at the moment and I have bought a SIM which has plenty of data, but the plan doesn't include SMS. I have tried activating iMessage again as my phone number is different, but it is stuck on waiting for activation. When I turn on iMessage it comes up with "Your carrier may charge for SMS messages used to activate iMessage."

Does this mean that iMessage uses SMS to activate? I have a little bit of credit for calls which I'm assuming if you send a text it uses a bit of it since the plan doesn't include SMS. 

Is there any other way I can activate iMessage?
To activate iMessage for a phone number, the device sends a silent SMS with a verification code. Carriers approved by Apple do not charge for this SMS. Activating without sending an SMS only activates iMessage for your Apple ID email address, not your phone number.