Game fourways bad service

I went game store fourways mall to pay my account and get some groceries, when I got to the cashier I told her I want to pay R500 to my game account and bill the groceries to my card. 4 days later I discovered that she deducted the 500 cash and added the R140 to my game account. So my account was not paid. I went to the store and was told the teller had made a mistake and I would have to pay my account being now being out of pocket R500. Pathetic service.