Billing twice

I was just at jet mart potchefstroom, the que was long and only one cashier was working at the time. When I got to the till there seemed to be some failure with their systems, and the cashier ended up swiping my bank card twice. After the transaction I decided to check my balance and found out that the transaction had gone through twice. I returned to him immediately and let him know. He said he was gonna do a reversal and the reversal declined three times, but he then went to speak to his manager who changed the story and said they cannot do a reversal because their eft system is down. The manager then came n told me that there is nothing that they can do, they cannot even refund me with cash because it's not their mistake but the mistake of the system. I certain don't remember swiping my card twice, it was their employee who did this. Now why do I have to be in convinced for their incompetence? They blatantly refused to help me and told me I would have to wait until tomorrow and if the money is still not there I have to go to the bank, get a statement which I will have to pay for, take it to then, they will email it to their head office and I might get assistance by around 2pm.