The best defense is this: don't recognize the PN, don't answer and call back. DNC doesn't mean squat ... these people breaking the law, using robo systems will just confirm that your PN is good and as the man said before will re-sell share, etc. Don't bother with the gov't, any gov't - state or fed, they're too busy passing bogus laws so that we can someday fulfill Obamba's socialist agenda and we will be the new Soviet Union -- talk about stupid people.
It would be worth putting up with these calls just to find out who these people are. No quick dispatch on my table, I would take my slow methodical time with these people.