Who called from 5086432711

Have seen this number twice in the last two days on my caller ID.  I tried calling back and the phone rang into oblivion.  No machine picked up.

I got a couple of calls from that same phone number before -- 508-643-2711.  On my caller ID it lists their number as private.
I have called them back before and there's always a busy signal.
I know when I picked up once or twice, no one answered.
Who knows?