Leaving aside the SIM card, there's no way to really know what the baseband is up to: https://www.extremetech.com/computing/170874-the-secret-second-operating-s

Leaving aside the SIM card, there's no way to really know what the baseband is up to: https://www.extremetech.com/computing/170874-the-secret-second-operating-system-that-could-make-every-mobile-phone-insecure https://www.extremetech.com/computing/170874-the-secret-seco...