Terrible service

Received two R250 vouchers for Checkers via their partnership with my medical aid. Went to the Muizenberg store.on 11 Jan to use the vouchers. Came to the till and the vouchers would not work, gave some message that the vouchers already burnt but I just got them and knew I did not use them before. They tried several things but nothing worked. The manager there, Jacqueline took my details and promised to log a query with their team and get back to me. It's now 5 Feb and I have heard nothing from either her or Discovery where I got the vouchers from. Discovery just tells me they looking into it but it's been almost a month. I need a refund or a new voucher that actually works sent to me. This has put me off going to Checkers, I never have issues with PandP vouchers.