Difficult to exchange

I am so disappointed, my friend brought clothes for my little girl it was her birthday by she bought wrong sizes I go to Rage to exchange they want slip, I mean it’s a present who put a slip on a present. Clothes are new, still with their prices I am being told I need a slip. I used to work at music and as long as the cd has price and sealed no problems. Now am stuck with clothes that does not fit my child