I get calls from this number frequently but they are automatically answered by my service and they never leave a voicemail.  I get notified of a missed call but when I return the call (blocking my number) the recording states the number is not in service, please try again.  I guess if they REALLY want to talk to me they will eventually leave a voicemail where I can figure out who they are.  Until then, I suppose it's not that important.