Bad Service

I would like to express my dissatisfaction with the purchase I made on Saturday. I bought a pair of Vans Sneakers which were a size smaller. When I took them back to the shop, I was told there isn't a size 3 at any shop. I understand that there is a no cash refund policy but in this case they cannot supply the item and I feel that they should give me my cash back so that I can go purchase the correct size somewhere else.