I recently purchased my TomTom720 from amazon. They claimed that you can use the car speakers to listen to the people that you talk to on your BT cell phone. I do know how to play MP3's over the car speaker using the FM transmitter. Obviously the microphone is on the TomTom, but is it true that you can listen to other people using the car speakers instead of the speaker on the TomTom? And if it is true...how do you set that up?