Return it to the seller for a refund from them - that's the only way you'll get that money back.
Contact Amazon, and say you're not sending it back to them, since the person on ebay sold it to you, and you need to return it to them for a refund.
If I were you, I'd pass Amazon the ebay Seller's detail as well - but there's no doubt some law against passing on a third parties details, even if they're likely a crook
