I have two devices, one is my phone, and one only plays music. I only ever use my phone as my phone, and my music device as my music device in my car, and both run over Bluetooth.

It is a crapshoot as to which role my car will assign to which device. Sometimes I have to put my phone in airplane mode so that the car won't try to assign it the media player role in Bluetooth settings. I'm not impressed.