Bad attitude of staff and unwillingness to help

I got to the Engen garage at Mayfield park at approx. 4pm on 12/08/2015, i cannot recall the attendants name, however I requested for R100 93 octane fuel which I decided to fill due to the fuel shortage currently being experienced. After a short while i checked the pump to see why he was taking so long to fill the fuel and to my surprise he had already filled up to R283.00. I then stopped him and asked him why is he filling more than what i asked and for to that i received the most appauling response. Firstly he insisted i pay the money because i asked him for R400, which i did not. I had three other people in the car with me who all heard what i asked for. He then wanted to fight with me, insisting that i need to pay the money for the balance of the fuel. I refused to pay for this as i did not ask for it and it is his duty as the attendant to be sure of what was requested by the customer. After not much help from management who said i could come and pay it at a later stage i again refused, as i could have just swiped my card to pay for the fuel. I then had an intense argument with the attendant who continued to insist that i pay for the fuel until the manager had to tell him to go