Who called from 3109753699

Has called me repeatedly over the past week, but leaves no message... What gives?

hello my  Name is Rachel Tracosas,
I just got a call on 11-28-11 at 7:26 from someone that i don't know and my cell phone said unknown caller and i am concerned about who it is

I am getting calls nearly every day for the past week, but when I answer there is nobody there.  Who is this?

This number has been calling for acouple days now. When I call back the number, it doesn't ring.

I picked up and was told that I won a sweepstakes.