Launching with iOS 8.1.
AT&T Seems to Be Extending FaceTime-Over-Cellular to All Customers
This, however, excluded a number of customers, including those with grandfathered unlimited data plans as well as those with the iPhones 4S. (Note, iOS 6, itself, can only supports FaceTime-over-Cellular on the 4S, 5 and iPad 3rd Gen or higher)
Tonight, Forum user kre62 noticed that both his iPhone 4S and iPhone 5 with unlimited AT&T data plans now support FaceTime over cellular.
In a recent thread we were discussing AT&T members getting facetime with LTE devices and tiered plans. However I noticed today that I have facetime over cellular and I have an unlimited plan on my 5.This finding has been confirmed by a number of users in this discussion thread -- though some users have been unable to activate it so it may still be rolling out to some areas. AT&T had said the original rollout for tiered plans could take 8-10 weeks. Most of the positive responses have been those with the iPhone 5 and grandfathered unlimited data, but the original poster also had luck with an iPhone 4S.
I just turned off my other phone, a 4S and turned it back on, only to find the switch flipped to ON for facetime over cellular. Both phones work perfectly over cellular.
I also checked a few coworkers phones, all now have FT over cellular.
Some users have had to completely restart their phones for the service to go into effect. There still remains a possibility that this is an oversight on AT&T's part. We are reaching out to AT&T for clarification on their policy.