iMessage activation unsuccessful

Hi. I've had my iPhone for over a year now, recently I bought a MacBook Pro. I had the iMessage linked through email and phone number. Recently (one or two weeks ago) out of nowhere I got the notification "Your carrier may charge for SMS messages used to activate iMessage". I click OK, wait for activation and every time it ends with activation unsuccessful. How do I fix this? I already called my carrier and asked about this, they said the do not control any apps I have and have not changed any charges.

Thank you for any help.