Quest Diesel contaminated

I filled my car with diesel at a Quest service station, near my home. On my way to Cape Town my car's engine completely shut down. I had it towed to my Toyota garage, after having all parts tested to find where the problem originated, the Weir test came back and the Diesel was contaminated. I had to pay R120 000 to rebuild my whole engine. I have been in correspondence with the service station since the 5th of October but they have not taken any responsibility for anything.