not trust worththy sales agents at mercedes

I Bought a demo Mercedes Benz in February 2019 at their Bryanston branch now merged to the Sandton branch. when i went to buy the car i asked the lady if there are any issues i should know about the car. she said the car was a demo car and there were no issues. 6 days down the line i noticed the following: 1. the car had aircon issues, 2. front centre mirror extended and was not told. i did not notice this because it was my first benz car and i though the distraction when i open the blinds are normal will all benz. 3. the brakes where making notice, i have noticed that the sales lady and the manager knew of all issues because when i reported them they were not surprised and just told me they cant help. i called the head office in march 2019 they promised to resolve the issues to no avail till today. i am currently driving a car with expired disk license because the car is not registered in my name. and when i ask the manager everyday he tell me that he will be sending his drivers and now he is not answering calls. the dealership or head office are not helping at all. is there a way you guys can intervene.