Mercedes benz

Hi my name is Bokang Lesejane I have a problem with Mercedes Benz centurion. On the 22 November 2020 I took my car for repair the engine light was coming on and off and the car was diagnosed and they told me I need to replace an oxygen sensor and while I was there I told them that around this period last year I brought my car to them because there was a funny noise coming from the right hand side and I was told it was a tensioner I need to replace it which I did and the noise didn't stop and they told me they will look at it after they have changed the sensor I even went to an extend of recording that noise as per Nelaan one of the manager at Mercedes I collected my car the next day which was Friday the 23 November 2020 after I was told the car was good I paid R10 600. On Saturday the light came on again and there was still there, on Monday I called them and they booked the car to be checked again on the 02 October 2020 and after they checked the car the told me they don't know where the sound is coming and about the engine light they need to put in 4 pins on the engine that is why the light is turning on and off the car was booked in today the 05 November 2020 and I had to pay for the pins now I am told the car has another problem I have to fix or change some coolant pump including its accessories which will cost me around R17k my dissatisfaction is that the car was there for two time in less two weeks with the same problem and yet the car waz diagnosed how did they miss this and everytime I have to pay money and my question is why in the first place this was not picked or in the second place and this year I replaced the water bottle because there were some leaks and was advised by them why they didn't pick it then I feel Mercedes Benz centurion are *********** and they are taking advantage of the clients I don't understand how they could have missed this because this year I took the car to them because it was leaking and the car was diagnosed and I was told it was a water bottle I am surprised that I am still sitting with the same problem and even with the noise I took it and was advised and still sitting with the same problem and yet I have paid money. Please intervene I need you assistance in this regards