Does anyone know how to hookup a cell phone through the audio system (the "TP" button on the radio)?

The manual says "If a telephone with hands-free operation is installed, the call may be routed through the speaker system." And goes on to explain how to setup the audio system for "AUDIO PH - Telephone call via the car radio."

I would like to use this capability. Any ideas what I need to tell my cell phone company to sell me, and then how do I hook it into the radio? My dealership gave me a blank stare when I asked about this.

Thanks