KFC- Charged me twice. Review on KFC, Infiniti 2 Mall, Malad West, Mumbai

I had placed an order at the KFC outlet counter in Mumbai for INR 286/- bill no 6970. The sale or the counter boy swapped the card and switched off the machine. Afterwards he started the machine and swapped my card again for INR 286/-. When I saw this I immediately pointed out the matter to the counter boy and told him that he had swiped my card twice but he refused. I ate my order and left KFC. After few days I was just going through my statement and I was shocked to see that the payment had been made twice from my card. I immediately contacted KFC and ask them to refund my money and they told me not to worry. They will investigate the matter and resolve the query as early as possible. Its more than 15 days now and its not been resolved yet. I also tried calling them multiple times but no use. How can they make such a big mistake. I want every customer who pay by card at KFC to check while the counter boy swipe your card as I think its a big fraud.