Rewards cards

on the 30th novmeber i bought grouceries and the was a competition for shoprite/ checkers rewards cards for which i have won a voucher, the was an option to continue, to view the prize i have won, nothing came though even went back to shoprite they called their rewards call center the lady who assisted me Zinhle *** said is, because i have used checkers rewards cards, that is why they i cant give me my voucher. shoprite /checkers rewards are using same rewards cards, if not why now because along ive using their same card. shoprite is failling their customers and i wish this matter can be resolved.