Sounds like he has opened a case.

You can go to your resolution centre to check and if so, all the details will be there.

If a case has been opened, but the buyer has put "change of mind" as the reason, then I guess you can accept it and the onus will be on the buyer to send it back.

If, however, the case says "not as described", then things are a bit more difficult.

Check there first and come back to us and let us if there is a case and what it says.