Some people are reporting that Call Of Duty: Zombies cant be unrestricted correctly and that people cannot play it online.

I verified the app myself and its working fine. I was able to play an online match while on EDGE.

Since the game CAN be unrestricted, but some people still report that it doesn't work, I suspect that either the port COD is using is blocked on some providers or that COD is blocking mobile internet IP ranges. If they do that, then probably only AT&T. But I'm not even sure whether they do.