If you post in Discussion > Selling you will receive a quicker reply.
This is a common issue. Most seller start by sending a message to the Buyer asking if they have contacted the wrong seller because the item shown is not yours.
If they open an IND case you must accept the return. When the return arrives, quickly contact eBay to see if they can help (do this before refunding).
Business Sellers have the option of reducing the refund by up to 50% in this case, and also protection from Negative Feedback.