Nearly a month after AT&T revealed its intentions of charging iPhone users for accessing FaceTime's video call service over cellular networks, the carrier has now announced that, after the release of iOS 6, users will have to sign up for the carrier's shared data plans if they want to use FaceTime over cellular on their handset.

Announcing the AT&T decision, though without elaborating any reason behind it, the carrier's spokesman said in an email that FaceTime over cellular will be offered by AT&T as "an added benefit" of its new Mobile Share data plans. However, the service will continue to be available over Wi-Fi for all AT&T customers.

With the Skype-like FaceTime iOS and Mac video chat service presently working only when the iDevices of both users are connected to a Wi-Fi network, the access of the service over cellular networks will evidently broaden the reach of the product. However, since FaceTime over cellular will gobble a lot of bandwidth, AT&T will impose certain restrictions on the service.

Meanwhile, pointing out that the shared data plans have essentially been created to meet the ever-increasing data requirements of the customers "at a great value," the AT&T spokesman said that the plans work in such a way that the more data the customers use, the more they save.

The Mobile Share data plans - set to become effective from August 23 - will be applicable to smartphones, tablets, and other Internet-connected devices, and will include unlimited talk and text.