Not delivering what is promised

I was in an accident on 15 March. On return of my vehicle I realised that the air conditioner pump is not working correctly. RARC determined that it was not accident related. They suggested they could replace the part . The quotation was R4500 for a second hand part, I accepted. they did not replace the part, but tried to repair it with a donar part. This did not work. I received a phone call promising a full refund on the work done. I asked if they could get a secondhand part and replace it. We agreed on a exstra R2000 for this. I took the vehicle back. Again they did not replace the part. I asked for the refund as I will procure a part myself. I was asked to collect the cash on the day I needed to procure the part. They did not have any cash and asked that I use my own money and collect the cash when returning from the transaction. Again they did not have the cash. I have been struggling for 3 weeks with this. I took the part to them to replace. Again they did not replace the part, but had a report stating that the pump in working correctly. The pump started making a noise at home again. I am not getting satisfaction dealing with them in the last 4 months on this