I’ll outline my scenario, just for fun.
The truck I owned at the time would lock the rear brakes easily. If I was going over an expansion joint and braking, for example, the rear brakes would lock. I decided to take it to the dealership (out of warranty, mistake 1). They looked at it, drove it, hooked up the scanner, and charged me a diagnostic fee. I think it was a little over 100 bucks. They decided the brake drums were out of round. I replaced the drums and the shoes myself. In doing so, I noticed the rear wheel cylinders had pressure on them with the brake not applied. My first thought is it’s a master cylinder problem. The issue persisted. I took the truck back to the same dealer (mistake 2). I told them the issue was still going on, and I told them that the rear cylinders were under pressure when the brake wasn’t being applied. They bled the brakes, charged me around $300 and sent me on my way. The issue persisted. I took the truck by a local shop and explained the issue to them. The mechanic says “bad master cylinder” immediately. So I let them change it and the issue was resolved. I asked them to state my complaint (rear brakes locking) and the repair to correct it (replace master cylinder) on the invoice, which they were happy to do.
So, I felt like I had a pretty good case that I should at least be refunded the original dealer’s diagnostic fee (they didn’t diagnose squat) and maybe a little off of the brake bleeding (since it wasn’t necessary or related to the problem). Anyhow, I got nothing. I showed the invoices to the service writer/manager and explained the situation. He said he’d call me. He never did. So, after a few days, I attempted to call him, but a lady answered the phone, asked who I was, and told me he’d call me back. After I called a second time and the guy couldn’t talk to me, I just told the lady I wanted to leave a message. I’ll buy my next vehicle elsewhere and I won’t be back, thanks. I never raised my voice or got real accusatory. I just took it to mean they had my money and really didn’t care to discuss it any further. I also decided if “diagnostics” meant taking an educated guess and throwing parts at it, I could do that myself for a lot less money and hassle.
It kinda hacked me off initially, but I got over it pretty quickly. Good luck.