Offered a credit note instead of a my money back

I bought size 5.5 of white All Star takkies and realized that they were not a perfect for me. When I went back for an exchange so that I can get size 6 they told me that it is out of stock and they won't get it again. I therefore asked for a refund since that was what I wanted. The lady at the shop insisted that that I take another item because their store does not DO REFUNDS. They then offered me. A credit note. There is nothing else that I want in their store I just want my money or the specific item that I went to their shop for.