Problen Mercedes since delivery in 2012

I have for three years now been battling with a b-Class Mercedes that broke down two weeks after delivery with a fuel pipe snapping in the middle of a busy intersection at peak traffic time. A car that has issues with brakes failing and being replaced almost every two to three months. This car has not been safe to drive on numerous occasion and I have been stranded on three occasions in unsafe areas of South Africa when my car stalled. the sales & service department have been aware of this from the onset. My car was taken in a month ago for the same problem and three days later it was back to square one , so currently I am driving a car that not safe. It the busiest time of the year for me in my business and I am on the road every day so when this happened I called in to book the car and I was told by service manager Marco that he cannot give me a courtesy car and that he has escalated to Mercedes Germany who is looking into this and until he does not hear from them he cannot guarantee when this will be sorted out for me. This is unacceptable because I leave for Holiday with my grand kids in two weeks time and cannot take the risk of driving a car that is unsafe on the road.