It seems to call out internationally either, to far east.

Over the past week I've received a series of calls on my cellphone from numbers with the area code and prefix 510-643-XXXX.  I haven't bothered to  answer any of the calls.   If this is the Cal Alumni Association they're in for a surprise because I'm not a Cal alumnus.  When I have attempted to call back I get a busy signal or continuous ringing.

This number calls twice a week at 8:30 or 9 PM and wakes up the whole house.  This last time, they left a message.  Young man saying, "Hi, (my name), we go WAY back.  WWWAAAAAYYYYYYYback!"  I am freaked out.