This number called me about three times yesterday evening on December 4th 2012 and didn't answer when I said hello. So I got fed up and said if you aren't going to talk then stop calling. And they did. They may have also left a message, need to check my phone 4 that.
I keep getting calls from this number as well. They will call and call and never leave a message. I do not answer or return calls from numbers I do not know and do not leave a message. Eventually they stop calling for a bit only to repeat the cycle a couple of weeks later. It's very annoying!