Wrong shoes size and they don't wanna give me my refund.

So I bought the Nike AF 1. I actually lay-byed it. I fit the shoes in the store and the shoes were not the same size. I bought 5 and a half and the box had 5.5 and 4.5 so I told the guy that these shoes are not the same size as the shoes were ordered from Wonderpark shopping mall. So they made a mistake of pairing the correct size. The guy told me to come and choose another shoes because he cannot help me with that one. I told him that I don't any other shoes except for that one. I told him to please refund me because it is not my fault that the shoes are not the same size and that I didn't even go home with them. He said that they do not offer refunds. Please help me get my refund back.