Car with tempered kilometers and Mohammed doesn't want to take responsibility for fixing the car

In May I was sold a BMW M135i a week later I discovered that the Kilometers had been tempered with from 200 000 to 155 000 I went to BMW and they confirmed that the Kilometers were tempered with. I took back the car to JOE'S AUTO VEREENIGING after about a week a Mohammed called and persuaded me to take the car and he will refund me cash R20k and I'm covered by them for 6 months should anything happen to the car they will fix it. I took the car and the money. 4 months later the car started having a knocking sound from the engine and I took it to a RMI approved workshop to be checked and and the report came back that we need a new or refurbished engine the car and I sent it to Mohammed he asked for some time to I gave him time and he started avoiding my calls and not replying to my messages... after leaving a number of messages at the dealer I eventually got hold of him and to my surprise he started swearing at me telling me that I took the car to be checked by another person so now there is nothing he can do and he is not going to do anything... they seem to be like a good car dealer until you have a problem. For such a big dealer to sell cars that have kilometers that are tempered with is a disgrace when you have a problem with that car 4 moths down the line they swear at you for no reason and now will to come to the party yet they said the car is covered by them for 6 months should something happen to it. It's also a Disgrace for someone of his(Mohammed) calibre to be swearing at me as an unhappy client like that and be avoiding their responsibilities like that while they are the ones that sold me a faulty car with tempered Kilometers