I don't answer calls from numbers I don't recognize nor do I return calls from numbers that don't leave messages. This number is similar to a number from the same Exchange I have gotten calls from earlier in the week. Both are VoIP numbers.
This number has called more than once. Caller ID says unknown name. Within the last twenty minutes they have dialed multiple times. When the answering machine picks up they hang up and call back. I turned the bell off.
Have gotten calls all day today (Sunday... who the heck calls on a Sunday?) and they finally left a 4 second voicemail. It's literally 4 seconds of heavy breathing. I've never been so creeped out by a phone call in my life.