Contaminated diesel tank

I went to pour gas at the BP, Fredenharry Rd, Cascades Road, Roodepoort petrol station and was attended to by one of the petrol attendants. I had no idea that he had poured petrol into my diesel tank, that is clearly marked DIESEL as per the attached picture. I don’t check the pump to see if the right amount is added, whether the cap is closed etc as this is largely a trust matter where I except the petrol attendant to know what he is doing, especially the fact that we frequent at this station so best to leave them at it. My husband drove the car, until the car came to a standstill. The car got towed and we informed the station, they settled the bill for the tow truck and was waiting for invoice to have the car repaired. The mechanic discovered that the tank was filled with petrol instead of diesel and advised that we needed to replace the fuel system. A lady called Antoinette disputed the amount charged for the repairs refusing to accept her staff’s negligence in violation to the Consumer Protection Act; and according to her there was no need to replace the injectors and the fuel pump. They accepted liability only to the extent that they are willing to pay, and this issue is still unresolved. She called for a meeting and came with a guy who she presented as BP’s mechanic. He questioned me, to the effect of how long i drove etc the information which I provided and according to him the car could not have driven that far without breaking down. How would I know this information? Any business operating within a framework is required to provide a fair, efficient, and responsible environment to its consumer and this has not been the case my experience.