Poor quality fuel at shell

I poured diesel into my car at Shell Philani in Umlazi Durban on the Sunday of the 10th June 2018. Soon after my car started mulfunctioning with jerking noises and movements from the engine. We went back and they did nothing to help me. I took my car to BMW that diagnosed a problem with some valves that was due to low quality fuel. To this day I have not heard anything from them. They damaged my car with their poor quality fuel. I have proof. My car was running well with an up to date service history until I went to their garage.