I have a 2006 A6 quattro and bluetooth. My husband took the car on a trip and said that the "mute" button on the MMI screen will not go off and therefore he cannot hear any music. The radio is showing the stations, but no sound. He had to disconnect his bluetooth on his phone, so he can place and receive calls. But, no radio sound. Any suggestions while on the road. He tried the scroll on the steering wheel, the on/off button near the gear shift- all to no avail.