Well has something serious actually happened and he blatantly ignored your call?


Because if not, I'm sure the earlier suggestion of "if I call its important, texts however can wait" is a good rule of thumb to communicate with him.


If he is however ignoring you consistently, when you clearly need him not to, then the logical solution is to not let him drive around in your car all Willy Nilly.


You need it, he doesn't, its all quite simple.


He's traipsing around entertaining a girl, they can use a bus or a taxi, same as other people who don't have their own vehicles.