Caller ID says "San Francisc CA".  They leave no message.

The message I hear is "We're Sorry. You have reached  a number that has been disconnected or is no longer in service.  If you feel you have reached this recording in error, please, check the number, and try your call again."

So we have a spoofed caller ID and the inability to be called back.  Smells like a SCAM to me.