Bad customer service at H & M.

I received a shirt as a gift. Unfortunitely it was small and I took it to return for another size and the cashier refused to exchange it. When you receive it, you usually take off the tag. Out of curtasy and customer service you would exchange it. The cashier lady said it was used. If the shirt cannot fit, how can you use it. The cashier was either stupid or dumb. This was at Gateway branch. Will never recommend anyone buying from the store.