Expensive repairs without fixing my problem-

I took my car over to this shop indicating there was noise with my car. The mechanic checked and told me that there was crack with my exhaust pipe and muffler and cost me $550. After I pay $550, the problem was not fixed. Basically, there were no problem with my exhausted system. It was related to my transmission. The mechanic didn't bother to properly looked into the problem and made me wasted $550 for an unnecessary repair - just want quick sales with no integrity and care about the customer. I have been using this shop for the last 15 years and spent thousands of dollar with them on my 3 cars. But after this incident (and another incidents of a $1150 repair), I will never bring my car there again. :(