Double charged payment

On the 12 I went to chicken licken at Keywest mall to buy a meal using my incentive card. The cashier said the transaction didn't go through yet the receipt which showed my order came through. Because I didn't have internet access in the shop I allowed for second payment. After leaving the store I realized I was double charged. I went back and spoke to the store manager who promised it will reverse if not I should come back the following day. On the 13th I went back and told him it hasn't reversed his response was it's not their fault I was double charged it's the system error. I have proof that the money hasn't reversed he didn't bother checking on that or see interested to help me. So where do I get my money back since the store doesn't want to take responsibility