1 AM got call with same message as Anon when I called back
 May 01st, 2007
Unknown name, unknown number called my phone at work... I answered, heard only a beep, and hung up. Phone rang a couple of minutes later, and this number showed up on the caller ID (no other info), with the same thing. I called the number back, and got a recording that said "to be removed from our calling list, please enter your 10 digit phone number." I hung up, worried that they were just fishing for live numbers, and entering it would just be an invitation to get more stupid calls...
 Feb 09th, 2007