African Bank rewards not redeemable!!!

I've been emailing /requesting call backs from African bank since August 2020. The reward vouchers that they offer no longer work. It has an error message that shows is voucher cannot be redeemed as campaign has reached its max redemption amount. To date no one has resolved this issue effectively n i have 6 vouchers i cannot redeem. Please note sending new voucher codes does not work as it still gives off the same message.