Some good news, Apple told Businessinsider that FaceTime will not use any carrier minutes, which means FaceTime will be free. This is possible because the FaceTime call makes use of VoIP and video streaming over Wi-Fi so does not use any carrier minutes. Till now you can only use FaceTime over Wi-Fi. Apple is trying to get FaceTime of 3G but they first need to decide how those calls are billed.
Apple told businessinsider: “The voice call ends as soon as the FaceTime call connects. The FaceTime call is over Wi-Fi so does not use carrier minutes.”