Park assist service message/onstar?

I was listen to the radio it was a aftermarket touch screen it always cut off every now and then I was in the process to replace it out with a name brand instead of a off brand this problem has been going on and off for a year anyway my radio started cutting off and on by itself then all of a sudden my park assist light stays on blinks every now and then and when I put it in reverse a red light is solid red but what puzzles me is I wanted to contact onstar to diagnose the problem and it wont work no customer service or no calls in or out is all that connected together before I go to dealership? Please help