I've had two calls from this number today.  I called it back and it appears to be from a company called Allconnect.  I used them to move my utility services.  Still no idea why they hang up when I answer.

That number currently belongs to Allconnect, a company that assists in moving utility services when you move.  They've called twice and both times hung up when I answered the phone.

No message either. Says All connect when you call.