Empty promise by Woolworths

I'm generally a huge fan of Woolworths but I keep getting asked to fill out my store experience and as a reward for good customers, as my self, there is a reward of R1000 voucher.I have now completed the questionnaire many times.At what stage should I be rewarded with the R1000 voucher? To be promised something and Woolworths not deliver on its promise,is disappointing.