Playing music in car & using bluetooth earpiece

There used to be an icon which would allow me to flick between my bluetooth earpiece, for handsfree phone calls and playing music through 3.5 jack plugged into the car radio (if I had a call while listening to music, it would change over automatically & cut off the music). Since the IOS7 update, this icon has disappeared. I can now only hear music through the bluetooth device if it is switched on, I have to turn it off if I want to listen to music through the car radio. Defeats the object of having bluetooth! My Bluetooth device is Plantronics M55. I have tried re-pairing it.

Any ideas?