Over on the apple support page (), they list the following solutions:
[After each step toggle FaceTime and iMessage off and then on in Settings > Messages and Settings > FaceTime.]
- Update to the latest version of iOS.
- Verify that you are connected to a cellular network and can send SMS messages. You need a valid SMS messaging plan to activate FaceTime.
- Ensure that FaceTime has not been restricted: Settings > General > Restrictions > FaceTime.
- In Settings > General > Date & Time, ensure that Set Automatically is on. If Set Automatically is on, but the incorrect time zone is displayed, turn Set Automatically off and then choose the correct time zone, date, and time. Then turn Set Automatically on again.
- Contact your carrier to verify that there are no restrictions on text messages. Blocks on text messaging will prevent iMessage and FaceTime registration.
- If you are unable to activate iMessage or FaceTime on a device after remote wiping it, wait at least 24 hours and try again.
I'm chatting with at&t tech support now, but it seems like (for me at least) the problem is on the carrier end. When they worked on my account earlier today, they completely messed up all my data related features. This is actually very typical for at&t.
I hope this helps!