BMW Midrand

I have experienced the worst service from BMW in Midrand, I took my car there cause it was showing an error regarding drive train where I was quoted around R20000 in January 2023. When I fetch the car after a week the person who suppose to test the car wrote under comments section that due to rainy weather he dd fully test the car. After a week of driving the same error occurs and I contacted the dealer where I specifically ask to speak to the manager but was told the manager is not in. BMW midrand ruin my car with wrong diagnosis as we speak my car is mixing water and oil after paying the R20000 to BMW midrand. The question is did I take my car to be fixed or to be damaged? They ripped me off honestly