Training gap must be fixed.

I got a game voucher on my phone and tried to use it at Game in Zevenwaght. The staff, including the manager confidently told me that I can't use it there even though the details I had from the Old Mutual loyalty program clearly says I can. I had to insist before anyone listened and then they did so reluctantly. It worked and then the apology. Can someone please address the training gap with the staff there, all the way to the management. A customer mustn't know more about your business and the relationships you have with other businesses.