I don't have my money, I don't have the shoes. I'm just sitting here with proof of purchase

I bought shoes at Europa art menlyn store. I was then advised they don't have stock but I can pay in menlyn store and collect at the Centurion store. I then drove from menlyn to Centurion, only to find they have closed already for that day. I then bought another pair at a different store which was open. I went to Centurion Europa art store the following day, i told them I got shoes somewhere else and therefore I need refund since I didn't even collect the shoes. The lady refused to give me my refund and told me that they can only give a gift card which I can only use at Europa stores. I don't need the shoes anymore, there's nothing I can buy at Europa art. Why can't I use my money to buy somewhere else? Why am I being forced to use my money specifically at Europa?