Poor Customer Service

After checking out at three different registers, at three different times, I realized I needed to break a twenty. I walked back to the cashier at the U-Scan I just left and asked her to make change for me. She said the only way she would make change was if I made a purchase. I tried to explain that I had and she insisted that it had to be at her register. When I asked her to call her supervisor, she was very displeased and became angry infront of me and my eight year old daughter at which point I had asked my daughter to walk away and sit at a bench. Supervisor comes over, tells the cashier to open her till, cashier rufuses and tells the supervisor to do it herself. This cashier had no respect for me, the customers she was dealing with at the time, her supervisor, and no sympathy for the eight year old girl standing near watching her mother argue with a rude employee after just purchasing her birthday gift!