Contaminant in fuel that was put into my vehicle by Engen Beaconhill

I put in fuel when my vehicle was empty on the late afternoon of 3 June 2018 ( I have checked the camera footage at the premises of Engen Beaconhill and there is proof that I was there). My vehicle started splattering and started to cut out. My vehicle then needed to be towed to Eastern Cape Motors. My vehicle has been checked by Eastern Cape Motors and have advised that my fuel tank was contaminated with dirty fuel (I have the fuel that was emptied as well as the spark plugs that were needed to be replaced). They compiled a damage report stating this. Engen came back to say that I am the only customer complaining and they are not at fault however my vehicle had been serviced and it only ever gave a problem after I had put fuel in. My spark plugs were burnt as well and they were new spark plugs that had been put in as it had been for a service. I am horribly dissatisfied in the recourse that was taken to address this issue.