Dirty Fuel

I had gone to Shell garage in Amalinda and topped my tank up to full that afternoon, the next morning my car doesn't start and I get reports from specialised folk to state that it was from contaminated fuel, the insurer is refusing to pay for the damages and say I must supply proof. So the fuel slip from the day before isn't proof, the reports stating that ALL 4 injectors are damaged due to dirty fuel isn't proof, the video of the fuel pumped out my bakkie isn't proof..... what is proof then? Filling my tank 2 weeks prior at my normal garage has never given me a problem and they FILLED it UP and now the insurer is saying give proof? what more proof do you actually need?