The only solution is to not use your smartphone as a telephone. Directly, anyway. Have a smartphone with no cellular account. Better yet, use a small tablet wit

The only solution is to not use your smartphone as a telephone. Directly, anyway. Have a smartphone with no cellular account. Better yet, use a small tablet with no cellular modem. Then do VoIP via WiFi hotspots. And for anonymity, do it through nested VPN chains. I know, that's not a phone, really. But that's life, these days.