MTN Upgrade including voucher, but no voucher received

I recently upgraded my cellphone directly through the MTN website. One of the key selling features was a R1000 Woolworths voucher. Upon upgrading, the assistant mentioned I would be sms'd the voucher which I could then use as I chose. I have subsequently received no such SMS, and each time I contact MTN, they keep saying I will be sms'd the voucher once the manufacturer has collated the details of the handsets. Needless to say, I still have not received this voucher, one month later. I have contacted MTN directly 7 times already, and each time they deflect and say the same thing - asking the assistant who performed the upgrade to contact me. Well, nothing has happened in a month, and I still do not have my sms for the voucher.