KFC

Hello, I received KFC coupon in mail. I used this coupon which says "10.99 for legs and thighs OR 12.99 for dark and white meat mix" to order legs and thighs ONLY at Elliott City MD store. However I was still charged 12.99. I tried to talk the manager and she said the computer showed 12.99 and there was nothing she could do. I consider this bait and switch false advertisement. Please let me know what you could do to fix this issue. Thank you
Product_Or_Service: Food