If you answer, like I did, they hang up after you say hello...

called 12/11/14, no message, added to block call list

It was a missed call for me and when I tried calling it back I got the very rapid busy signal.  Probably solicit type call

The very same thing happened just now to us.  We thought it was someone calling to harass us about how rotten OU was doing - so I called it back several times, but it always rang once and then went in to the beep-beep-beep that means "overload" (too many calls coming in :()

I did not answer the call from this number and they did not leave a message. I blocked my number and called right back and it said Verizon Wireless National Customer Service... I don't have Verizon as my provider, so??? I called back a few minutes later and got the busy tone as someone else has mentioned they got.