No return policy. No explenations. bad attitudes

I asked the lady at the till to look at my size cup of my bra, she did but said in a bad attitude, there isn't one. I asked okay can I go fit it? She said yes. Still had to wait for door to be unlocked. Eventually put it on and the cup size was too small. Took a wrong cupsize again and paid. She didn't give me the no return policy speech and I was off. Next day I saw cup size was bigger then the first one. So I return to exchange it. So there's a no return no exchange policy that I didn't know of because why can I fit it there but at home not? Still won't return my money or exchange it. I have two bra's that are too big for me to wear and a store who won't help their clients with the proper manners and respect.