connectivity issues

24 yukon Denali. had problems with Google not always connecting. several hours on phone with onstar  to correct that. then no apps on rear screen. after waiting couple of weeks for escalated issues to be resolved. they got apps on rear  screen  but it says contact onstar for streaming plan. but I already have streaming plan.  they  called me again to do more resets. and now no apps on rear  screen. they called me. again and said just take it to a dealer! what! this is no longer warranty and dealer will start changing parts. maps work and other Google work. but no apps and streaming on rear screen. There has got to be a way onstar can fix this! been going on to long!