Very disappointed

I bought my sister a dress, and unfortunately the dress didn't fit her well, because it was meant to be a gift I had removed the tag but kept it. When we tried to go exchange or get a refund truworths randburg refused. I'm so disappointed in them, I had the receipt, packaging and everything and just because I had removed the tag, which I still had they said they can't take it back. What am I supposed to do with a dress that doesn't fit