Question for Fluo

I bought pants on 28/12/16, when I got home I did not like the color, I could not go before the holidays to change it so today I went To change the color, but I do not have the receipt! But there is the label on the pants and everything is very good except the receipt! Then the cashier's lady refused to change it! And she was very wicked ... I do not think there are stores that do this, it's not the first time I buy clothes from any stores and I exchange them Without the receipt! !