Caller left no message. No Caller ID

No message. Likely to be spam.

There is a pattern here.  This spammer has been using numbers in the series: 408-797-30xx.  Hangs up without leaving a message.

I've gotten a lot of calls from this area code in the past month. I have a call blocker and the calls are blocked, and I add them to the screen caller list on my home phone. The ones I've said "hello" to have always been scammers.