very disappointed

I send the product for sale (because they said the product was sold). They checked the product and sent it to the buyer. After weeks, they inform me that the size was different from the description and that the buyer had returned the shoes (although the size is clearly the same as shown in the product photo on the website). They kept my shoe ... they didn't pay me and they didn't send the shoe back to me (as it would be correct). I asked him to send me back and get no answer. I have already sent several emails and no one responds.