Wrong item delivered - vinted refusing to give refund

I ordered some thermal base layers, the item that was delivered was paperback books! The seller claims they didn’t send books and I (stupidly) binned the packaging. I did take a photo of one of the delivery labels (with the corresponding references etc) but vinted claim I needed to have another picture of a different label!

Anyway, they have refused to refund me and closed the case.

From googling, I am not sure that they can do this … does anyone have any advice on how to challenge this?