PacSun complaint: Refusing return

I purchased two t-shirts for my son and did not notice one of the t-shirt has a tiny hole in the front. My son wore it to school for one day and told me the shirt is damaged, but he didn’t see it in the morning before putting it on. I took a shirt back, but store manager Francis Hang refused to exchange this shirt for the same one telling me that once it was worn( even once) he will not take it back. I told him that I purchased damaged shirt and did not notice it in the first until my son told me. He said I have to have a proof for that! After I asked a higher management business contact number, he also refused to give it to me. I feel this is completely unacceptable to treat customers like that. We come to this store expecting quality merchandise to be sold for money we spend, and this is very unacceptable to put a customer to this situation. I expect this company stand for quality and I don’t want to buy damaged merchandise and not being able to return it. I hope upper management will take it seriously and solve this issue.