Unsatisfied with customer service

I purchased this shirt from Polo, but unfortunately, I noticed a yellow stain on it after wearing it for the first time. I attempted to return the shirt, but the cashier refused to accept the return because the original tag was no longer attached. I had removed the tag before wearing the shirt, as I did not notice the stain at the time of purchase. I understand the store’s return policy; however, I believe the stain was already present when I purchased the shirt. I was also disappointed by the cashier’s attitude and felt that I was not treated respectfully while trying to explain the situation. I would appreciate it if you could review this matter and consider a reasonable solution, such as an exchange or refund, since the item appears to have had a defect at the time of purchase.