I get calls to my mobile from these numbers. The phone only ever rings once. Even that ring is truncated as if the call is disconnected as soon as it possibly can be.
As it's clearly not a real person there I never call back. I figure if a real person really wanted to talk to me then they would let the phone ring out. Heck they might even leave a message.
So - more interesting - does anyone know who these people are? Leave a comment if you have any ideas? Double leave a comment if you know how to stop them!