MyWorld Reward Voucher not received

I have an African Bank MyWorld account which promises a reward after swiping the card ten times. On 4 May I was sent a sms with a unique code which allowed me to redeem my R150 grocery reward, and was informed that I would shortly receive another sms with a wicode voucher. I have still not received this voucher. This makes me feel that African Bank is not a bank to be re**** on.