Bad service from Mercedes Benz east rand

I took my car into Mercedes Benz East rand mall for it had an engine warning light, they diagnosed the car and sent me a quotation with all that need to be fixed in the car, I gave them go ahead and I have paid R52 230.00 for the work done into the car. I took the car from them when the repairs were done drove a car for one day then the engine bearing ceased and they are now refusing to repair my car saying it is not their fault while they were the ones worked on the engine of my car, furthermore the technician whom they sent to asses the car told me straight that the guy who was assigned to work on the engine of my car has caused that to happen as he has no experience to work on the engine. I logged my complaint to mercedise benz SA and they are no helping me either since November 2020 my car is sitting there in their yard because they towed it back to them and the manager denied to fix it.