Poor customer service

So I went to Skipper Bar on the 28th of September 2020 to buy some items and I found a guy who works there and he was assisting me as I was shopping. I also bought under wears but wasn't too sure of the size that I should buy because sometimes we tend to forget our sizes, he asked me what size of pants I'm wearing and I said I'm wearing size 34, he advised me to take size small of which I did.He also assisted me at the service desk and then I left the store after paying and when I got home I asked my aunt who is a tailor to measure my waist with a measuring tape and we realized that the undies would not fit they are small and I even checked my older under wears to see the sizes and I saw that the ones I bought were small.I went back to the store to make an exchange and spoke to the same guy that was assisting me and before I even finished explaining he just said to me I cannot return under wears.He had an attitude because he didn't even look at me when he was talking to me.I feel that he misled me because he is the one who advised me to to take this size,why didn't he worn me first before I bought the under wears that I cannot return them because he saw that I was not sure about the size. He was supposed to advice me to to go home and be sure of the size.