AT&T Inc. (NYSE: T) dismissed what it called knee-jerk reactions to its plan to limit Apple Inc. (Nasdaq: AAPL)'s FaceTime to its Mobile Share data plan users, but several groups are taking their complaints all the way to the Federal Communications Commission (FCC) . (See AT&T Reserves 4G FaceTime for Data Sharers.)

Free Press , Public Knowledge and the New America Foundation’s Open Technology Institute have now officially warned the wireless operator that they plan to file a formal complaint with the FCC in the coming weeks.

Both Sprint Corp. (NYSE: S) and Verizon Wireless have confirmed FaceTime will be free of charge on all their data plans.

But, AT&T is taking a different route. The carrier said in July that all its customers will be able to use FaceTime over Wi-Fi as they always have been, but to use it over the cellular network with iOS 6 they would have to subscribe to a Mobile Share data plan. The carrier's regulatory chief, Bob Quinn, addressed net neutrality concerns, calling them wrong, in a blog post last month. (See AT&T Plays FaceTime Defense and AT&T Joins Verizon in the Shared Data Pool.)

What AT&T and the advocacy groups are fighting over is the FCC's Open Internet rules, published in 2010, that state that mobile broadband service providers cannot block apps that compete with their own voice or video telephony services. AT&T's argument is that since FaceTime is preloaded, it has different restrictions from downloadable apps, to which the groups collectively say, "Phooey."

"It’s particularly outrageous that AT&T is requiring this for iPad users, given that this device isn’t even capable of making voice calls," Free Press Policy Director Matt Wood wrote in a statement. "AT&T's actions are incredibly harmful to all of its customers, including the deaf, immigrant families and others with relatives overseas, who depend on mobile video apps to communicate with friends and family."

The FCC requires groups to give 10 days' notice when they plan to file a complaint. AT&T has yet to respond to the warning.

— Sarah Reedy, Senior Reporter, Light Reading Mobile