BP muizenberg terrible service

I am disgusted at the poor service at BP garage in Muizenberg Capricorn. I asked the attendant to put a certain amount in only to find out he filled up the tank. In questing why, he said he never heard or thought to reconfirm. The manager on duty then agrees that I should pay the full amount. This is ridiculous that I should pay for something I did not ask for at the mistake of another. I have the names of both attendant and manager and would like someone to address this. In a situation like this the attendant should be paying for the extra he put in.