Laptop return

I ordered a laptop and was delivered on the 21 July and found out it's not the one I need, I contacted homechoice for return they told me they can't take it back as I've opened the box, how will know it's the one I want if I can't see it I'm not the expect when it comes to electronics, I need a laptop with the DVD writer for my studies. It's unused, still in the box. Please take it back and exchange it