First message this buyer and have them confirm they are messaging the correct seller. Mistakes can happen.
If they insist it is, they need to open a case for item not as described.
You fully refund on receipt of your item, or when eBay tell you it has been posted back.
If then you find it is a different item posted back to you, or a damaged item different to the one sent out, you then appeal the decision of that refund with eBay Customer Services.
