Firstly, I presume you HAVE actually sold something?!
You must have the email address of the buyer, email them and ask if they're having trouble paying with Paypal. Could be the real buyer is nothing to do with these (alledged) scammers.
Have a look on ebay and get the buyer's address (as seller, you can), then email and ask these people who and where they are. Again, the scammers could just be 'hijacking' a geniune finished auction. No match on address - it's dodgy.
Or, give them your work address to send the cheque to. Or, you can still do '
Poste Restante' for free.
Don't give them a phone number, they don't need it.
Just insist they pay by Paypal - no payment, no goods. Sorting out the Paypal 'problem' is up to them, not you.
You do seem to attract problems :(