The Gateway 500S BT is capable to work as a media player (Gateway music functions are active only) or just a phone module. In order to turn a main function OFF (phone or media), you need to use the DIP switches on the hardware.
There are 6 DIP switches on the bottom of the Gateway. Switches #1-2 are for setting the car configuration (Mercedes, BMW, Audi, Porsche). DIPs #3-4 are not used.
For disabling the media function (Gateway music menu) of the Gateway, you need to turn DIP switch #5 OFF.
For disabling the phone part, DIP switch #6 needs to be turned OFF. You can choose this if you want to keep the factory phone module of the car.
After changing the switches, you need to turn off the whole car with closed doors for 10 minutes to finalize this new setting.