******* refund policy

I went to Rage Northgate on the 14th November to buy clothing for my daughter, we came back home and she fitted the clothes and they were too small for her, I went back to the store to refund the clothing, as they didn't have bigger sizes, I could not exchange the clothes. I was told that Rage doesn't refund clothing on promotion since I bought the clothes on promotion weekend they will not refund me, they rather give me a gift card but I don't want a gift card, because I didn't buy with a gift card, I made a purchase using my hard earned cash and I want my money refunded in cash or my bank account so that I can buy clothes for my daughter in other stores where I'll find sizes. They called head office and head office told me that it's their policy it's in their receipt. The worse part is that you only get a receipt that has their policy after you make a purchase, is this policy even legal, why did they not explain this to me before I made the purchase.