Mercedez Benz negligence cover up and overcharging for work not done

I've received absolutely disgusting service from Merc Rosebank and MBSA. My car was serviced in May last year. The car was leaking oil. I fixed the oil leak but the car was still losing oil with white smoke from the exhaust. They fed me a bunch of garbage as to why the car was smoking. This has been going on for 8 mths. I took my car and replaced the aux battery but it is still not working. The engine light started coming on. They fed my a load of garbage again as to what was wrong. My car eventually got stuck when I left the dealership one Friday evening in early Feb. They assured me my car was safe to drive. The car switched off about 8 kms from my home. They towed the car to the dealership and my car has been there since. They informed me that the DPF was gone and then two days later they tell me I need to replace the turbo charger. In my meeting with Merc last Friday they confirmed both DPF and turbo charge needs to be placed. They told me that the head of their technical team was looking at this and a report will be sent to me. In my meeting they send no such report will be given. I showed them the invoice where it states that the turbo charge was removed and reinstalled. This is the exact same time I stared to have my problems. They now claim it was an error on the invoice and they are happy to refund me but I must still pay R180K to fix my car. It was through their negligence that caused this issue. Furthermore the oil leak that was fixed was not because oil was leaking through the turbo charger which caused the smoke and now ultimately damaged my turbo. It is equally shocking that a brand of mercedes benz can overcharge customers and get away with it but claim admin error to suit them.