My car was having issues that needed their diagnos...

My car was having issues that needed their diagnostic tool to figure out. I told them I was a single mom and between jobs. I was worried about the outcome of this visit. They had my car for several days and I thought they were being nice by providing me with a loaner car. They finally called and told me what they thought was wrong with the car with a recommendation to replace a battery and all 6 coil packs that cost me $1500. I learned afterwards that what they should never have recommended to change all coil packs at one time. They don't go out like that, and it did not fix the car. I had to take the car a second time and noticed they charged me almost $200 for a rental car that I never asked for. When I brought it to their attention, they said they would reimburse me part of the rental fee and I would get a check in the mail in about 5 days. That was about 2 weeks ago. I called back twice to find out something and they don't seem to know anything and don't call me back. So they have charged me hundreds of dollars for unnecessary work and parts as well as a rental car fee, and now offered to reimburse under $100, but won't send a check or answer my questions when I call.
I have never complained about anything but I think people should know what to expect if they have any work done at Hickory Toyota.