The number was issued by Pac West Telecom Inc.  Email them at abusepw@pacwest.com
or call them directly

Pac-West Telecomm, Inc.
4210 Coronado Avenue
Stockton, CA 95204
(877) 626-4325

They issued the number - they can shut it off.

More information on the ownership of this number

Search Results for 415-449-7606
Status:    Ported - Inter
Activation Date:    02/13/2015 02:27 PM, EST
NPAC SPID:    4899    NPAC SPID Name:    Onvoy:4899 NSR/1
Operating Company:    ONVOY LLC - CA (668G)
Rate Center:    SNFC CNTRL
LATA:    722 - SAN FRANCISCO CA

Please contact www.onvoy.com/contact/report-abuse for more assistance.

I too got a call from them.  Apparently they are the same scammers who pose as a focus group on craigslist to get numbers and then they just keep calling you from different numbers.  Today there were at 415-449-7606 but I have as list of 20 something numbers they call from in the SF Area so they are probably cloaking their real number, or constantly changing their number.  If you block them expect them to call in about a month with another nearby number and "PRIVACY" in the caller ID listing on your box.  I'm giving my list of the their former numbers to the cops - with such a list they probably can identify who they are from all of the phone company records...