Poor customer service

I bought some clothes for my daughter on 21 July 2021 at Jet Heidelberg Mall. When we got home my daughter fit on the pants and informed me it is to big. Today 24July when i want to exchange it i only have the slip for the card payment with me. The original slip is gone. I am informed that i am not allowed to exchange the item. So i am stuck with a pair of pants my daughter cant use. Manger pulls up her shoulders tellking me i can do what i want she dont care.