reward vouchers on my world account dont work

When you have an my world account we have a perk where you get shoprite vouchers when you use the card more than 10 times per month. I have two vouchers as below , but when I got to the store the vouchers did not work. WiCode : *** WiCode : *** I wrote to the African bank rewards department and they don't respond. be aware they may be louring people to open accounts and then not action the reward promised.