Swipe Double

I went for a drive through and bought food for about R73 and i used a gift voucher to pay and I do remember there a struggle with the cashier couldnt process the payment so it was about 4 people tried and tried and eventually they managed to get it right, not knowing they have process the payment twice and that was neglegence of them beacause they could have picked that up and sorted it out then and there. Im very upset as i tryed usung the card again knowing there is a balance of more than 70 rand and now i have to check what happened to my balance i have proof on all this.