Who called from 6504312759

Called at 3:11pm and didn't leave a message. Tried to call them back, but operator said "number is not signed to anyone, check the number again and call back."

Received a call from this number ((650)431-2759) and they did not leave a message. I called it back and it said the number was not assigned to anyone yet. Whatever!!!

Gotten three calls from this number since Feb 20th. Once I did answer and dead air.

Called but left no message.  How can I block these unsolicited numbers?

They called me this evening at 9:39 eastern. It's annoying how these spoof numbers have no consequences to face.