Getting a repair shop to refund charges

I took my Subaru Forester to a repair shop in my neighborhood with a check engine light. Their diagnostics indicated that I needed to replace the O2 sensors. When they attempted the repair, they called to notify me that in trying to remove the old sensors they were probably going to destroy the cat converter and it would then need to be replaced. (They said that the sensors were coming out crooked and the threads would strip.) I posed this problem to this fine site and followed andrewj’s advise to take it to the dealer for the repair. I did that and they made the repair with absolutely not problem. The first shop charged me $110 to diagnose the problem. Now I want to go back and ask for a refund. Do I have a chance in hell? I hate confrontations, but I also hate being ripped off!! (By the way, the repairs at the dealer were covered by my after-market extended service warranty and I only had to pay the $50 deductible. The original repair shop had also cleared the job for the warranty coverage (GE), but GE would not, of course, cover a destroyed cat converter.)

I think that you are out of luck on the diagnostic charge. You did agree to it to begin with, right?

Well, not exactly. They did not mention it up front, as I was also getting an oil change and had asked them to check on the check engine light. I paid the oil change and diagnostic charges after I decided not to let them destroy my cat converter. I just wanted to get out of there and pursue my options!

They did a diagnosis of the problem, so they deserve to be paid.

Ok, they did an oil change AND a diagnosis. They still deserve to be paid.

Just think of how much money you could have wasted on them.