dud fuel causing car to cut out while driving

I put R100 petrol in yesterday and my car was fine, half an hour or so after that the car started cutting out while driving and is now not able to idle. i approached the manager who was very obtuse and said to me that it must be an electrical problem (the car is an old Toyota with a carb and has no electronics) I told him this and he said to me that he fills thousands of cars every day and that he has a petroleum certificate. i then told him that I would never use his fuel again, this morning the car started smoking and smelling of oil so i can only surmise that they are mixing diesel and fuel. I have changed the fuel filter and kept the old one so that if testing is necessary I have a sample. I intend on taking this as far as I must.