If you're planning on splurging on a new iPhone next month shortly after the release of the company's newest iOS, you'll find something new on this iteration of Apple's wildly popular smartphone: video calling over FaceTime on the cellular network (as opposed to only Wi-Fi, as in previous versions).

FaceTime is of course a video conferencing software application and protocol developed by Apple for iOS-based devices and Mac computers running Mac OS X 10.6.6 and higher. FaceTime is supported on any iOS device with a forward-facing camera (all iOS devices released since the iPhone 4 was released) and on any Mac computer equipped with a special FaceTime Camera.

If you're an AT&T customer who pays for one of the carrier's shared data plans, FaceTime on the cellular network will be a feature you can use. If you're a customer grandfathered on the company's older unlimited data plan, or you're tied to one of its tiered data plans, you may be out of luck.

Doesn't sound fair, does it? It may not be legal, either.

The New York Times is reporting today that a non-profit Internet law group called Public Knowledge is claiming that AT&T is violating government net-neutrality rules set by the Federal Communications Commission (FCC), by blocking a service that potentially competes with its own. The FCC's Open Internet Rules dictate that cell phone providers cannot “block applications that compete with the provider’s voice or video telephony services.”

AT&T says it's doing nothing wrong, since FaceTime will still available over Wi-Fi for customers without the shared data plan.

“FaceTime is available to all of our customers today over Wi-Fi, and we’re now expanding its availability even further as an added benefit of our new Mobile Share data plans,” said AT&T spokesman Mark Siegel.

Being able to use FaceTime over a Wi-Fi connection on an iPhone, however, is not related to how the service is used on a cellular network, notes the New York Times, which predicts the issue isn't over yet.