Brand new Mercedes Benz keeps on cutting out

I purchased this year a brand new Mercedes Benz over a million rand from Mercedes Benz Pinetown. Since I have purchased the car, the car I have had 5 instances where the vehicle just cut out. The vehicle just came back from Mercedes Benz Pinetown after more than a 2 week period of tests. The issue is still not resolved. I have written previously to Mercedes Benz South Africa and Mercedes Benz Germany. Mercedes Benz South Africa has phoned me several times, BUT the fact of the matter is the problem is still not resolved! I have honestly reached the point where I am insisting on a new vehicle. The frustration I have with my current vehicle and absolutely limited effort from Mercedes Benz South Africa is beyond ludicrous. Below is my email to Mercedes Benz South Africa and Germany, I have no email response from either one of them: 14 August: I am based in South Africa. I am writing this letter to you since I feel my hands are tied here in South Africa. The service I have been receiving from Mercedes Benz South Africa has been ridiculous. See correspondence below with Mercedes Benz South Africa Johannesburg. My vehicle is currently standing now for 2 weeks at Mercedes Benz Pinetown, the car keeps on cutting out. The vehicle has been in for repairs several times and is still not fixed. The past 2 weeks the dealership have been driving my car around trying to find the fault.. THEY STILL have not found it!! How long am I supposed to be patient?! First I do not get proper feedback, second I am not in favor of them driving my car around for 2 weeks. I paid over a million rand for a car that I have no faith in! I have been driving Mercedes Benz since 1984 and never have I been disappointed in the brand as I am now. I have reached the point where I am insisting on a NEW vehicle.