unfortunately, you’re not likely to ever find them. the world of voice has been infected with SIP services such as skype. they use throw-away accounts and exploit compromised systems owned by clueless users to proxy through. it’s only occasionally that they unknowingly utilize a honeypot planted by law enforcement as a proxy that they ever get busted... and then 90% of them are freekin Ukrainian, Russian or Chinese and there isn’t a damn thing you can do about it.
Still needs to be on record in case we return to a constitutional Republic some day.