I have purchased all my cars from Al Serra in the ...

I have purchased all my cars from Al Serra in the last 30 years and loved them. That was until now. Car on for service and they "lost it" for 2 weeks or more after finally duplicating the problem. I got no return calls from my messages requesting updates during that time. When I finally got ahold of service guy he apologized and said would reprogram ECM. Then nothing again. He failed to write up another repair order AGAIN. Had to start over again trying to duplicate the problem. Was told GM wouldn't pay to keep putting parts on it without a code. Call dropped while talking with them and I received a nasty message that he didnt appreciate being hung up on and if I was going to talk with an attorney they would no longer work with me. That is great as I have no intention of ever going to them again. If a mechanic cannot figure out repairs without a computer telling them what's wrong they are simply parts changers.