I believe this is the scam where they hang up after 2 or 3 rings in hopes that you will call them back.  In their demented minds, they think they are circumventing the Do Not Call registry because you (the "callee) called them back.  ZZZap!  Blocked you, scammer.

Comes up on phone as "Name Unavailable."  I don't answer it. Sometimes I pick up the receiver and slam it in their ear.  Think I'll literally start "blowing the whistle" in their ear.

Caller hangs up without leaving a message all hours of the day and into the night!

Call several times a day for the past week.  I answered once with no response on the other end.

I received call from 334-923-6237 several times within a couple hours.  One time, some how, voice came in as a 3rd party during my call with another person!   How was that possible?  The light on my phone lit up and message on display said "extension in use".  I have AT&T U-voice, through wireless modem.  I called the number and got recording that call can't go though as dialed.