Return and exchange

Last week Saturday my sister had bought 3 dresses for me but because she couldn't try them on due to the covid restrictions she couldn't tell if the sizes would fit me (we're similar in size)

When she got home and gave them to me jt didn't fit nicely at all so 6 days later I went back to the store but don't hsve my receipt because my sister gave the dresses as a gift to me There's no receipt but all the tags are on the dresses, never worn them besides fitting it in

I went to the SAME pep store and they refused to help me All i want to do is to exchange the dresses for different sizes

It's so upsetting because they go out of their way to be unhelpful