AT&T: FaceTime Over Cellular Free For Mobile Share Data Users, Unavailable To Everyone Else
The feature will be 100% free for users of AT&T's new Mobile Share data plans, which have proven to be a fairly terrible deal for all but a few folks with larger families. But for everyone else? It's not an option, period. There's no option to pay a fee to use it, nothing. You either switch your data plan to the awful new Share plans, or you stick to Wi-Fi for FaceTime.
If you're still clinging to AT&T, it's time to ask yourself: why?