I was once ripped off by a mechanic in a medium-size dealership (where I had actually purchased my car, new.) I simply called the owner who soon sat down with me, listened to my case, called the mechanic who presented his side, called in another mechanic who agreed with me, and then handed me a check for full reimbursement with sincere apologies.
In other words, go to God. Don't go to the angels.
I note that the owner had his name on the dealership. Very helpful.
And another story....
I have a late-90's Subaru Outback. Many of these engines develop piston slap. The dealership I had purchased the car from refused to fix the problem. I soon moved, went to a different dealership, mentioned the problem, they checked it out, and immediately offered to repair the problem. Needless to say, they have my respect and business now.