KFC - E voucher claim issue

KFC service is very bad, it is not first time I am using E voucher for stores like pizza Hut, Domino's, but I have tried first time E voucher to KFC elpro mall Pune ** april ** * to *pm after order selection I have shown the coupons to KFC staff, he has entered all the details and after several trails he said KFC system having issue to accept the coupons, you can try this coupon after some days, I have come out without getting any order, and today ** jun** * to **pm I have visited to KFC chinchvad Pune, and shown the coupon details to staff, he said this coupon already being used, hence proved that KFC is having very worst service, and victims are like me suffering in system issues, and there is no any acknowledgement from KFC side that once your system up need to inform customer?
You must check CCTV footage of that day and time, and check system issue, I want positive feedback from your side, or else I will need take farther action against KFC,