Block the calls. Ask your phone company how. If they aren't helpful:
For your land line - buy and install a call blocker. They are available on Amazon and at Best Buy for less than $50
For your smart phone - you probably have a call-blocking ap pre-installed. Use it. Or download and install one.
For your older-style cell phone - put the pest in your contacts list and assign them the ring tone "no ring". That will send the calls to voicemail without disturbing you. You'll have to empty your voice mail occasionally.
Noted phone number in my cell phone's caller ID. Answered since I'm also in the 408 and could be getting calls from some unknown numbers due to a family situation. Took a couple of seconds for them to respond, all the while hearing conversations in the background (typical call center atmosphere). Guy started talking about an offer that I could qualify for due as part of the Council on Renewable Energy. I cut him off and said that I already have solar (which I really do) and said "thank you" and hung up on him. Hopefully they will note this in their records and I won't be bothered by them again.
And yes, my cell phone is listed with the DNC registry but I know it doesn't do any good.