USB repair

I purchase a car at Mercedes-Benz Constantia Kloof on 21/08/2019. Upon collecting the car, on my way home, We realized the USB was not working. We informed the dealer and return the car. After the repair, when testing it was still not working. We returned the car again. It took them more than a month ( August-September) to repair the USB in the car. Clearly, there was a major problem with repair of the USB. They end up loaning us a car for September 2019. When the car returns, the left side of the USB was working whereas the other side(right) was not working. We were tired of the back and forth of the car, so we ended up accepting the car. I started experiencing challenges with the left side. The port was loose even though it is working. I notify the dealer when the car went for a service and requested them to repair the USB. The car is still under a maintenance plan, I was told to pay an amount of R3800 to repair the USB as it was repaired before. Mpho( Sales Rep) said I can take the matter with Mercedes-Benz South Africa if unsatisfied with the dealer's outcome. I logged a call with Mercedes-Benz South Africa. Upon their investigation, I was told the USB was replaced shortly after purchasing the car last year, so I must pay to be repaired. They further said I must complain to Ombudsman if not happy with the outcome. My point is the USB was not working when purchasing the car. It's the responsibility of the dealer to check all before releasing the car to the client. Why is it difficult to repair it as the first breakage was not my fault? I was not expecting this service from both Dealer and Mercedes-Benz South Africa. Mercedes-Benz must repair the USB without any payment from me.

Regards Tebogo