Called my cell. I don't answer unfamiliar numbers. Left no message.

Same here

Robot call from Arcadia, CA offering extended warranty insurance.  It's a scam.

I have a carpet cleaning company located in Chicago, so I assume 99% of all numbers that are not from Chicago are spammers.
Unless I'm wrong and someone from California heard that we do really good work and wants us to drive 3000 miles to get to the house so they can pay us for $5000 to do the job!

Best thing to do with these numbers is answer and immediately disconnect, then block the number in your call history. They just called me and that's what I do when I do not recognize a number. They will never bother you again! Then you can always Google the number.