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.