Robert's Paint Collision

Last October I had a car accident on the 35, and robert's paint-collision took my car to repair the trunk. I live in Cedar Hill, so I wanted to fix my car somewhere near to where I live, but they didn't want me to take my car away from them and begged me to leave the car with them because the county didn't give them a lot of cars. They told me that they were gonna put a used part because they supposedly they were not able to find it new; however, I don't know which part is used because they didn't show it to me, they just called me to say that they were gonna put a used part. They took a whole month to fix my car and told me more than three times that my car was done and once I was going to pick it up, they said that it wasn't done and come back the next day. On June, I noticed that the paint of my car's trunk started to come out. On August, I called them to see if they were gonna be able to fix it, they said to go to them so that they can check it. Once I arrived to them, they checked it and said they were gonna give me a rental car, fix it for free and that they were going to take maximum four days to fix it. However, they were not able to fix it that day, so I needed to go back in two weeks so that they can fix because they were already behind with other cars. I went back on August 22, they gave me the rental car and said they were gonna call me the next day so that I can pick it up the day after (in total I was gonna have the rental car for three days). On the same August 22, they called me to say that the car had a bump and that they were not gonna fix it for free anymore, we had a fight on the phone and told me that I needed to give the rental car back that same day or I was gonna pay the extra days. Today August 24, I went to give the rental car back, and they made me pay 87.43 for the extra two days. In conclusion, my car DOESN'T have any bump. They don't want to take any responsibility of their bad work. They don't care if I call the police or the lawyer or whatever person. I even called the police today because I didn't have to pay the extra days of the rental car, and they even said bye to the police like if they were friends, so I DON'T recommend them at all.