What can you do if you take your car to a mechanic and he doesn't fix the problem, but still wants to charge you? Are you obligated to pay him for labor if the problem isn't fixed?
You will still be charged to get your car checked even if it doesn't fix the problem. It sucks but it's what usually happens. But if you take you car to the shop you use regularly, you may get the service for free.
I think most shops make it a practice to tell you their diagnosis and not start any work until you give your OK to do the work, which creates a contract situation.....
It never hurts to talk to the management. They want satisfied customers, and if you are not satisfied, they will likely make a good faith effort to earn your satisfaction.