Report them! I worked for a Rain Soft distributor, doing telemarketing. May the Lord forgive me, but I needed the job. Eventually I was promoted to calling existing customers for annual maintenance, but ended up trying to talk them out of suing the distributor. This particular outfit sent out ex-cons to unsuspecting families to browbeat them into buying a 5k whole house water treatment system.
The typical scam is that they set up booths at fairs and trade shows, and people will fill out a slip for a drawing. Even if you are on a "do not call list", filling out that entry negates that. Those "leads" are recycled forever. Renters, single parents(in most circumstances), retirees, and a couple of other categories, are not considered. There has to be income potential before the mark is given the sales pitch. These all come scripted, and woe betide you if you go off script.
This is one of the harshest ways to try and earn a living. As for posing as a government agency, that is a crime. I hope you have some way to track down whoever is doing this, and turn them in!