I am getting the same thing. A call from 213-232-2307 and it turns out to be no one. I have missed the call mostly because it is in the afternoon. When I went to return the call it said a different number 215-922-3253 and that it was disconnected. I am calling the phone company right now (on hold forever) to see what I can do about it.
Same thing here in Denmark. Received call today, no one answers in the other end, then, after a minute or so, hangs up. Waste of time and bandwidth (since we use IP telephones .-)