Bad Custimer Care

Highly irate. Purchased school shirt for my son at Pep Seadoone. There were purchased on the 21st of January. My son is 17 but small built. When purchasing the two shirt i advise the lady who was assisting me. She said its ok ma as long as you keep the receipt you can always return if they don't fit. Sent his brother today with the receipt. And the lady in charge refuse exchanging them, She says there are untidy and don't have packaging. After long communication she decide better the child comes over and fit the shirt to avoid the exchange, Like why? If i am the parent and saying its okay you can give me this size why does she want to punish me?