pick'n'pay refused to take my giftcards

So I bought a pick'n'pay gift card on Bitrefill.com and I went to my nearest pick'n'pay in Thulamahashe, Bushbuckridge. I asked to pay using the gift card, as the cashier was helping me, she said that the gift card needs a confirmation of some sort. This is when she called some other lady at the store by the name of Audrey, who also seemed to not understand how giftcards work. Audrey said that they don't accept gift cards because I could be trying to commit *****, at this moment I became upset because I have used giftcards before without a problem. I insisted on talking to the manager, who's Name is Rodney. But he did not attend me, I just heard him talking to Audrey that they don't accept giftcards which are not brought by a physical card. I told the lady that a giftcard is a girftcard, what matters is the code but they did not help me either because I could be a ********* to them. While on the other hand the manager completely ignored me, and there was nothing I could do, so I left. Pick'n'pay Thulamahashe gave me the worst service I've ever gotten from a grocery store, and also labeled me a "*****". Now I have a giftcard I bought with my money which I can only spend at pick'n'pay but the shop won't accept it, so my money is lost. Why does the shop have giftcard on online platforms but stores won't accept them?? What am I supposed to do now?