Shell garage

On Friday 25/05/18 i went to fill up my car at Shell auto Brackenfell. R595 was out of the ordinary. So i queried... I have 35l tank but now im billed for 41l. In my head this does not make sense. I dont drive my car till its empty...EVER!! The most ever is 33l when i fill up. I asked the petrol attendant if hes sure he cleared the clock before putting in my petrol. He laughs then proceeds to tell me petrol went up. Which had absolutely nothing with what i was saying. So did i end up paying for a previous customers petrol?