Trouble exchanging item with my gift receipt

<p><span style="color: #666666; font-family: 'Source Sans Pro', Verdana, Geneva, sans-serif; line-height: 20px; background-color: #ffffff;">I've been given a gift from earth child (truworths sister company) and I've been told that I can change it for anything from either truworths, uzzi, earth child etc and now when I went to change it with my gift receipt they've told me that they cannot give me a gift card to purchase at the other stores and I can only change it for something at the earth child store even tho I went with my receipt. I'm really disappointed with this</span></p>