Sovereign BMW Vereeniging

I am beyond ungrateful for the service provided by Sovereign BMW Vereeniging, I took my F22 series 220d for strip and quote. I was experiencing some black smoke when accelerating, I took my car to Sovereign BMW after quoting me roughly 12k to repair the faults and after repaired they suggested that I must drive 1000km and return it to check it again. I was then told that problem it is not what they repaired and they must quote me on the new fault yet from the beginning i took it for strip and quote before any repairs was done. I tried to take this matter to BMW South Africa till today I haven’t got any assistance.