I will only say one thing since my family is in the business. People sometimes expect mechanics to be magicians and they aren't. Great mechanics will diagnose properly about 95% of the time (read on). Usually your issue will be taken care of the first time around, for those sometimes complicated situations its a step by step procedure because most customers don't have an open wallet to try and fix every problem. A complete misdiagnosis that didn't begin to solve your problem or simply abuse (that's why you should work with one you can trust) is something else though. I wonder what kind of relationship, if any, there was with this mechanic.