Poor service from Mercedes-Benz South Africa

I bought a c180 in 2018 and for the second time since driving this car I experienced a loss of power in the engine what they term "misfire". The initial resolve a year ago was to change injectors . Last Thursday I had the same problem again and I am told injectors need to be replaced. All this for a car that is still fairly new. I have requested a courtesy car from Mercedes-Benz SA and I am being told I must wait for escalation meanwhile I continue paying a hefty installment for a car with engine problems that the company cannot solve. They cannot even tell me why this keeps re-occurring and from where I am standing , I suppose they sold me a faulty car and do not want to acknowledge this. The least they could do is to make sure I don't suffer any inconvenience seeing that the car is still under warranty. I am very disappointed with the Mercedes-Benz brand at this point.