wooden_flower Volunteer Community Mentor.
You should have the buyer return what they received for a refund, then let them purchase the correct item again.
If you want to risk the buyer not returning the item, you can buy a return label on a site like pirateship.com, and send it with the correct item. A really sneaky buyer could also open a not as described return and get a full refund after you send the correct item, and just ignore the label you sent in the second shipment.
