Some of the scammers have run shady phone companies like CallerID4U [0] specifically meant as "bulletproof hosting for robocallers". I could see them branching out into the CA business.
CallerID4U seems to have gone (has been put?) out of business, at least. My Asterisk box hasn't received calls from their prefixes (which I blacklisted) since 2015, and their website's main page returns a 403 Forbidden. [1] It took a bit of hunting with the Wayback Machine to find a good shot of their page. [2]
Spot-checking on telcodata.us, it looks like their prefixes/thousands groups have gone to others as well. 253-245-2xxx now belongs to CenturyLink, for instance, and 425-336-8xxx is unassigned.
Much like "unsubscribe" links in spammer emails, they even had a helpful "Click here to register a complaint and put your phone number on the DO NOT CALL (DNC) list" item on their web site.
CallerID4U seems to have gone (has been put?) out of business, at least. My Asterisk box hasn't received calls from their prefixes (which I blacklisted) since 2015, and their website's main page returns a 403 Forbidden. [1] It took a bit of hunting with the Wayback Machine to find a good shot of their page. [2]
Spot-checking on telcodata.us, it looks like their prefixes/thousands groups have gone to others as well. 253-245-2xxx now belongs to CenturyLink, for instance, and 425-336-8xxx is unassigned.
Much like "unsubscribe" links in spammer emails, they even had a helpful "Click here to register a complaint and put your phone number on the DO NOT CALL (DNC) list" item on their web site.
[0] https://800notes.com/forum/ta-705926565a74ba5/callerid4u-inc...
[1] http://callerid4u.com/
[2] https://web.archive.org/web/20130310040410/http://callerid4u...