I haven't answered because the ID says invalid number.  We get a call from this number at least twice a day.

Yeah, they continue to call but, I have Phone tray Pro best investment I ever made, it blocks ther call and shows up on my computer screen. The software uses a voice modem from Amazon.com $30 Software is inexpensive but, saves me answering the crank calls!

I am on the DO NOT CALL REGISTRY - SO PLEASE DO NOT CALL

...  and you are demanding they not call you, at this website...  why?  You're using a screen name that isn't associated with you in any way, for safety.  That's great.  But telling them not to call you, here?  Do you also go to the movies and, during coming attractions when they say "Coming soon to a theater near you, " do you think they know where you live,and they're talking just to you?"  (Wondering why she'd tell the scammer not to call here, on this website...  does she really believe they come here to check...  know who and where she is...  and then obey her?)

Touché! I was going to write substantially the same thing myself, but seem to have run across a kindred soul instead! But, I was also going to address the "Do Not Call List" side of the issue. And so I will.
Too many people totally misunderstand the function and intention of that list. It's not your own personal call blocking set up against everyone who calls you with whom you are not acquainted. It's not like an invisible shield to protect you against every criminal and scammer out there.
What it IS, is a list assembled by the local - usually state - government where you live, of people and their phone numbers who do not wish to be contacted by legitimate, legal telemarketers who wish to call residents of the State or Commonwealth, and in the case of the National list, of this country, territories and protectorates. Citizens must voluntarily submit their information to the holder of the list in order to be a part of it.
Then, any legitimate, legally operated telemarketing firm MUST BUY THE LIST covering the territory in which they wish to call, and scrub their own call lists of every name and phone number​ on the DNC list, before they make the first call. A list of those types of firms and organizations which are exempt from those requirements, is found on the website covering the list in your state.
It also covers how to report calls received that obviously are in contempt of that law, both from legal telemarketers who are apparently not aware of, or who are flaunting the law; and this kind as well, from the obviously illegal scammers and criminals who are flaunting the law for their own criminal purposes, no matter cost.
THAT is what the Do Not Call list is for. It grants everyone who's on it a certain amount of protection and advantages that are not provided to those who choose not to participate. And that's the key - active participation. Everyone is responsible for helping to make the law work, just as you are, under the law, required to do certain things in order to help make other laws work as well.
Find out from your State - usually the State Attorney General's office is the operating force behind it, but it can vary - just exactly what the law requires of telemarketers who wish to make the calls where you live; the ones who are exempt, and there are several; and what is expected of YOU to help make it​ work. You must be proactive, not just sit around and expect everyone else to do all the work. Good Luck!