This number calls and never leaves a message.

I received a call from this number on Sunday, June 22, at 4:06 p.m.  They did not leave a message.  I called back (using call block).  I reached a recording which said that they were attempting to take a short survey and would call me back at a more convenient time.  I did not leave any information.  There is no convenient time, since I am on the "do not call" list.  As any regular user of this site knows, however, the "do not call" list is useless.

they keep calling me, it is from Chicago, I just ignore the caller id.  

It's blue cross blue shield. I contacted the number on back of my insurance card and spoke with someone regarding the number. Said to not answer and that they would forward the info to their call center

Caller ID lists them as Blue Cross Blue Shield. When I pick up (I do so because they are my insurance company so I wonder if it's something important) there's no one on the line. This has happened twice now.