Bad service/insulted

Hi I handed in my car to be repaired at Mi-Tech in Blackheath a month ago. My car couldn't start as it catted off while I was driving. I towed to them and managed to speak with Ashley the boss. The following day they called me to check if I'll be able to pay R6600.00 for striping the car to find the problem, I said yes but I was shocked that they didn't diagnose the vehicle. After a week, I called them, they said they will send me a quote. A week later, a quote was sent quoting R20 568.00. We agreed on it and I paid the 50% deposit they required to buy spares. They said they will make sure that everything will be 100% when I get my car. I kept on calling, I get the same promise that they are doing their best so when I get my car it must be 100%. It's been a month now still not done. I called today to check as they promised last week, to my surprise, it's not done. They want to quote me again for other staff that they think it was caused by the problem they claim that they fixed. I was angry as I can' be without my car for another month. The owner insulted me by telling me that he can see where the problem is, he said it is because I'm not willing to pay him and I don't sound like a have money to get my car fixed. I had to put the phone down as I could sense that the guy is insulting me. After an hour I called them and ask to put back my car to the state that it was when I brought it in. They refused. I can't deal with them anymore. I want them to refund my deposit and I'll go and get my car fixed somewhere else.

Thanks you.