Won a R500 prize which they now refuse to honour!

Filled in a Clicks Community Survey and a few weeks later received an email from them that I had won R500 Clicks Cashback and it would be paid into my card shortly. After 6 weeks and no cashback I logged a support ticket with them and waited another 3 weeks with no response. Phoned into the callcentre and was told the ticket had been assigned to the incorrect team (Marketing apparently) and would be reassigned. About 2 weeks later received a very short email stating that I never completed the survey and therefore didn't qualify for the prize, despite having actually completed it and having an email confirming that I had won a prize. Another 6 weeks and multiple emails to them which are all being ignored.

Clicks, you have disgusting customer service!!