It depends on the law where you live. In the UK, where I am, if someone sends you something you didn't ask for, you're entitled to keep it, and they're not allowed to ask you to pay for it afterwards. I believe you can send it back to them at their expense, but I could be wrong about that.
In your case, I'd ask the company for proof that your granny ordered the book (which of course they don't have). If they still want the money, and you have any paperwork that proves she returned the book, send them a copy of it (not the original, because they'll probably "accidentally" lose it, or claim they never got it). Failing that, most places have services where you can get advice on how to deal with companies who are trying to rip you off. I'd start with your local library or government. They probably won't be able to help you, but should point you in the right direction.