Request for refund

In September 2021 I laybyed a Nike sneaker for my son size 10 and took it out in October 25,2021 in the Xcross trainer at Hemingways mall, East London . When it was time to wear them in December they were already small I kept them since I was in the villages for December holidays. I came back in January 6,2022. I took them back to the shop I looked around and I couldn't find anything I asked for a refund I was told they don't do refunds and that they can only do a voucher card for me. I accepted that thinking maybe I would get another sneakers soon enough.

Since January, I've been going back and forth to the store there are no new stock since January. Every time I go there I'm told to come following week I feel like they are playing with me.

I would really appreciate if I can get the refund now we are in mid April still no new stock from the shop.

Kindly assist