Vehicle service and repair workshop did not replace part as agreed instead they tried to repair

I took my car for repairs at Service Tech Middelburg on 28 February 2020 and I was told my car has damaged water pump and thermostat housing. It needed to be replaced. The owner of Service Tech told me the original part of my car will cost about R16000 and my motorite warranty was only going to cover R6000 and I had to pay the balance.

I spoke to the owner and explained to him that I might not have that kind of cash he must rather get another supplier which is Goldwagen middelburg that is selling cheaper Volkswagen parts. Then we came to an agreement that he will do so. The new quotation was R10379, the warranty approved the claim and had to pay the R6379 and I had to pay the balance of R4000 I took my car in for repair and all was well until about 3 months later when my car started losing coolant again and I had to top up every week. Since then I have been checking water everytime and never thought it can be the pump cos it was recently done. On 29 April 2021 I took it to a different dealer and was diagnosed discovered the pump is damaged. I authorized them to remove it and I will buy a new one. And only to find out that the pump that was in there is the original pump of my car and it was never changed. I called the owner of Service Tech and could not find him but explained to his secretary. She said he will get back to me but he did not. On the 30 April I personally went to Service Tech, the member denied all this and said he needed proof and I showed him pictures that my car was stripped the previous day and what I discovered. He showed me an invoice of an engineering company which he took my water pump for repairs. He did not change the pump but tried to repair it for R1300 and charged me R10379 AMD told me he replaced the pump which he did not...

Please assist me in this regard, I need my money back from Service tech Middelburg. Their service is very poor. I had to replace the pump again and paid a lot of thousands. The very same pump I thought it was replaced last year February.