Rental car nightmare

Rented out a vehicle online and confirmed availability at Lanseria Airport collection 6pm. When about to collect got a call that the car is not available and they will look for one in the branches around. Got a call a few minutes later that vehicle will only be available around 9pm. As I was stranded had to wait and finally at 9pm managed to get the vehicle. I had a very early trip the next day so as I was on my journey I tried to put the aircon on and it did not work. I phoned the branch and reported this to them and they promised to look into getting me another car. The guy I spoke to phoned me back and indicated that there was another car in the Fourways branch. I indicated to him that I was not near Fourways as I was on my way to North West. I asked if there was another branch there that they could do the replacement with. He promised to check at Klerksdorp and get back to me. This never happed. I then returned the vehicle and all was in order depite my unhappiness. Now a few months later I get a bill on repairs on the vehicle and phoned the claims to understand and they indicated that the aircon condenser was damaged and I was being billed for it, a fact I am disputing.