Do not, I repeat, DO NOT close the dispute under any circumstances. The seller is trying to take advantage of you being a novice seller. It's a common tactic of Asian sellers so don't fall for it. Only close it after you've received a refund. If it's an Asian seller, don't fall for the "I'll send you a replacement" tactic, because you'll never see it. Refund only.
Once you've received the refund, come back here and someone will tell you how to close the dispute. You can just leave it and it will eventually time out, but if you've got a refund, better to just close it and it's done then.
If the seller is insisting on closing the dispute prior to refund/return, escalate the dispute as soon as you can. It may say something like "ask eBay to step in and help". It's taken out of the sellers hands then and you should get a refund really quickly (often instantly).
