Fraudulent return advice

Buyer returned empty mailing bag (item is much larger than a mailing bag)

Return Reason: The item is damaged but the box or envelope is undamaged

Buyer Comment: The product does not match the description

I've messaged the buyer to let them know we received an empty mailing bag with their return address on it. I've asked them if they will be sending the goods back separately.

What else to do right now?