Poor service at Mercedes

I have a Mercedes GLC 220d (Reg no: NT 67943) 50000km and I had taken it twice to Mercedes Benz in Umhlanga to fix the rear window which does not close full, and which needs to be repaired and the navigation system shows wrong mileage for instance from Ballito to Zimbali the distance is 2km however on the navigation it shows 3****m. Nobody could fix this problem. During the last service the air filter was not cleaned. I cannot lock my car due to the window that wont close, and I cannot wait 1 week with the hope that this time it will be fixed. Usually these repairs do not require more than 30 minutes and I do not understand why I have to drop off the car at their premises for 1 day, provided that they have the spare parts in house. I cannot understand why Mercedes does not have a service organisation in Ballito, which is the second fastest growing area in South Africa and where all the car brands are available except Mercedes? A car is a commodity and therefore a service is very important and must be improved.

Emanuel