REFUND REQUEST ASAP

I went to the pep store in brackenhurst yesterday afternoon .The cashier swiped my FNB CARD for R 821.60 for a purchase .She then tried it twice and said the transaction failed . though the money went off the account . an sms was received . This kind of approach made me feel humiliated as it seemed as though i didn't have funds in my account . I was then asked to pay cash which i did . So I paid twice . If the speed points are not working , this needs to be resolved .I want my money back by the close of business today .PEP NOW HAS MY R 821.60 which belongs to me and not THEM .