i think the do not call list is merely a way for the government to sell your number to scammers. pretty sure the scammers use the list as the phone numbers they should call because LEGITIMATE businesses wouldn't dream of cold calling people on the list.
Yet another Search Engine Optimization scammer. The robocallers wouldn't be doing this if it didn't work. I get dozens of these calls a week, but rarely the same number twice, and never the same number 3 times. That is because the illegal robocallers are using cheap VoIP numbers or spoofed numbers. You don't have to be in the United States to get a US number with VoIP. Scam a few people, shut down the number, repeat.