Bad service and manipulation to pay for mistake

I had the worst service at this panel beater. Firstly I was supposed to be at the garage at 8am, when I got there around at 8am I asked the mechanic/painter (forgot his name but he said he is a painter) if I can pull my car into the garage so they can start working on it. He didn’t agree and asked if I can call his boss which I did and the boss (Chris) told me they will start working on the car and asked if I can give the guy the phone so he can confirm. The painter said he will start working on it in a few minutes and then later changed the story that he is waiting for the boss. The boss only arrived after 10am (he told me he was traveling from Fish Hoek to Rylands). Then started with the car as all my paper work was already sorted such as quote and authorization letter from the insurance. The insurance was only paying for my roof dent. I then asked Chris if he can quote me separately (as I was going to pay out of my pocket) on two minor dents at both sides of my back doors caused by other peoples doors. He than quoted me for R2300 of which I didn’t have and he later asked if I can do one side for R1100 and I agreed for fixing the dent then paint and polish it. I then asked if he can try other side to pull it flat even if its not painted as to keep the bill at R1100. Chris agreed but said he will try something different that will not require him to paint the doors and then briefed his painter about the job. Then only started working on my car after 12 midday, the same painter doing my car was also busy doing other cars and would take breaks in between to do my car. After the roof dent was painted and waited for 2hrs to dry the paint so they can start polishing. The polishing started around 5pm, but before they could begin the painter asked me again what did his boss say about the polishing, even though I was confused by the fact that he is asking me this question. I told him that Chris said they must polish the roof only as the side doors were first going to be fixed (pulling out the door bumps using some machine). The next thing I saw the painter polishing the whole car and with another dude. Chris saw this happening and did not stop them, this was during the time he was busy pulling the bump on my right hand side back door. He then instructed another guy to polish the door as he wanted the door to be warm so he can use the machine to pull effectively. Then immediately he left to attend other clients that came to fetch their cars leaving everything in operation without saying anything. The painter continued to polish the whole car and now the time was after 6pm. Chris came back again after 35 minutes telling me to pull out and that I can go but he was not even finished with the job. I didn’t understand him so I parked the car outside the yard to make way for other cars to be parked inside the garage. Then I saw Chris still busy with clients and apparently one client was not happy that his car was not yet finished. After finishing with the client I told him I need to leave as I have an emergency and before I leave I need to know if I should come back so he can finish the job. Chris then said I can go but wants to talk to me about the additional cost and called me to his receptionist and explained that the painter/mechanics had mistakenly polished the whole car and that I have to pay because he can not do that for free. I told him I am not paying for that its not my mistake and its not what we agreed on. He asked me “then who was supposed to stop the guys from doing the mistake” and i did not understand this question and I saw it as a way of trying to make me pay for their mistake.