Dollar Tree

I bought some stuff a week ago, I decided to trade some stuff out later that week. I come back to the same cashier who bagged my stuff. I had bought nail polish and it wouldn't ring up so she ran some other stuff up to take a space of the nail polish. When I go back to trade the nail polish for something else she says that she never scanned other items to equal out the nail polish. So i left with what she claimed she didn't ring up and no receipt. I called in the same day to to talk to the manager she said that I could come in two days to trade for nail polish out. I went in today to do so i'm watching the lady who rung up my stuff turn around and started whispering to the manager. The manager says "you can go pick out the items to return" i do so the manager is supposedly off at lunch and the original lady said I couldn't trade in the items without the receipt( that she took and kept). she was rude and ignored me as she saw i was waiting in the other line to get the trade happening. The managers name is Tracey, the cashier is usually working most day. I'm honestly very pissed at this whole situation i just wanted to trade in 8 things