Checkers Xtra savings competition lie

In Dec 2020 we downloaded the Xtra saving app and it had the spin and win competition and we won a R1000 voucher and it gave us a code and also it was to expire only on 31 jan, we even got messages stating that, so i went to redeem this, filled my trolley up everything came to R2744, and i knew i had the voucher so all was good until I'm at the till and they tell me the voucher is not valid, waited for more than a hour with no luck, was given the choice to leave the full trolley or pay the full amount luckily i had the enough money that day and needed these items, the workers were polite and apologized but told me that they will escalate the matter to Xtra savings department , i went back in Jan still no response, they called the Xtra saving dept from the store and explained again only to be told they would get back to us the only thing i have is a Ref no. 465364, this is not on to date we got no response, what if i didn't have the money that day and only went with the voucher to make the purchase, all we want is what was promised, don't have competitions or reward programs when you cannot uphold your end of the deal please.