Prepaid billing solutions for push-to-talk in a wireless communications network

An apparatus for providing prepaid billing solutions for advanced group services in a mobile phone network, comprising:

• a mobile phone network for making calls between mobile phones, wherein the calls are initiated by call setup and in-band signaling within the mobile phone network and voice frames for the calls are switched between the mobile phones by at least one mobile switching center across bearer paths in the mobile phone network;
• and
• a real-time exchange that interfaces to at least one mobile switching center in the mobile phone network to provide the advanced group services therein;
• wherein both the real-time exchange and the mobile phones that use the advanced group services communicate with each other using the call setup and in-band signaling within the mobile phone network, and the real-time exchange switches the voice frames for the advanced group services between the mobile phones across the bearer paths and through at least one mobile switching center in the mobile phone network;
• and
• wherein a real-time billing mechanism is provided for a prepaid subscriber of the advanced group services.