Bad service

I went to dischem yesterday while i was paying asked the cashier if I have any money as my points were high but she said no with an attitude but after paying checked the receipt and found that I had some money on my rewards card. I was really not happy with the service i received its not even about the money its about the way she was speaking the lack of interest she showed. very unhappy she looked like she didnt want to assist me at all. When I was done paying my sister payed for her stuff and happen to want to return one of the items as she was short of money but the lady said its not possible she must ask me to pay for her which I found very rude cos it was none of her business.