Had calls like this several times and hung around once for a "live" person. Had one guy (foreign), who I interupted and told him I am on a no call list, and I am to be put on his no call list and don't call again.  He told me he has every right to call, it is legal, and he can do it anytime he wants. After a few "rounds" he hung up, and I didn't get too many calls after that, BUT ... they are using cell phone numbers (it seems) ... my cell phone is on the national no call list as well.  So .. they continue to call, and don't care about the federal regulations as they shut down and open up another number.  
Oh, by the way, try to call back and can't complete the # as dialed...interesting and should tell us "buyer beware" right there!
Like the air horn idea, but then they'd probably try to sue (but, then again, you'd know who it was).
SCAMMERS ... Phishing ... that's all they are trying to do is rob you!!!

Unsolicitrd call. Option to be removed from call list is not offered.

Didn't answer and no message left. I'm in the do not call registry. Please make it stop.

They call me 2-3 times a week. When I tell them not to call my number they hang up.

I got a call saying I  would receive money from the government that IO could use any way I wished and  I would not have to pay it back.