A friend of mine recieved incessant spam faxes despite doing the above.
So she decided to reply to their fax number with a stack of black paper with a post it saying "Remove my number (...-...-....) from your database immediately. If I recieve 1 more fax from your company, you will be reported for DNC violation."

She never heard or saw from them again!
"Hell hath no fury like a woman scorned" LOL.
Oh, an eFax # is awesome too.