AutoNation Ford Miami

I took my Mustang in for an oil change and to check why the check engine light was on. They said that the light was on due to all the damaged wiring from an old accident, before I had the car. They did the oil change and then offered to trade it in on a new Mustang but when I said no to their offer I found that my air con and engine overheating indicator was now not working, something that worked before I dropped the car off. The refused to fix this as it was all "accident damage" from 3 years ago? I took it to an independent auto electrician and he fixed all the problems. I did contact the General Manager of AutoNation Ford Miami but he never responded. Beware!