Whenever my iPhone connects with the Bluetooth carkit that is integrated in my car audio system, the iPhone switches AirPlay to the carkit and thus sends all audio to the carkit instead of the iPhone speaker. However, when I'm listening to the radio, those sounds are essentially lost.
So, whenever I start the car, I have to manually switch AirPlay back from the carkit to the iPhone, to make sure I will hear text messages coming in, for example. That has become a lot easier with the advent of the Control Center in iOS 7, but I would like to disable the automatic AirPlay switch to the carkit. How do I do that on my non-jailbroken iPhone 4S running iOS 7?