Customer Etiquette

I purchased a pair of Vans sneakers for my daughter who does not live with me, it was a month later that she received them and we realized they do not fit. I asked if I could exchange for a bigger size. I was bluntly told No, by the store assistant. Now I can understand the 30 day return policy, however it is the manner in which the assistance said No and this being a rare case I strongly believe it could have been handled on its own merit. What further aggravated me was her saying to me that even though they still have stock of this item and it is still in the condition I bought it, there was no way the exchange will happen.