They ask if you can heard them so they have it on tape of you saying YES.  So if you buy into their pitch and provide them with info about yourself, they have your YES answer to something else.

Did not answer and it left no message.
   If you dont recognize the name/number, DO NOT ANSWER. If you happen to answer, DO NOT RESPOND IN ANY WAY; NOT BY VOICE, SELECTED NUMBER OR CALL BACK! After all, they are scammers and you dont really know what you answered or consented to do, give or buy, for which your number may be billed.
And don't waste your time with cute answers...there's no satisfaction and they don't care. They just move on to irritate or hook the next sucker
    Scamming and phishing only works if there is a market (target, sucker). They are bottom feeders that have no limits, conscience,  mothers, or legislation  (DNC) except you.
   Legitimate caller will be identified, will leave a name, message, and call back number, giving you the option to respond.
   I wish all the TV stations would run programs at prime times on scams and cautions; how to report and deal with them. That would be public service in public interest, and hopefully, make these scammers into real losers.

Just got call didn't answer. Red here scam blocked!

Now they are calling me on my cell phone in addition to my landline! So annoying.