Motor mechanic repairs

I have taken my car to svds motors for over heating problem where I had to pay 9000 and the car after a week is started over heating again I took it back to them as they said to me maybe it is not what they fixed maybe let them check what could be the problem then I asked what was the diagnostic payment for as they said to me the diagnostic machine is for electrical problems then I left the car later received a call from them say it was a heater velve then again I payed R3500 plus the parts I bought again for service and that heater velve I drove with it for 3 weeks and it is not my daily used car it over heated again in November I paid R12000 now in January is the same problem over heating! This guy are ****** they don't know what they are doing as they saying now it will be another thing