If you have problem in Face ID because you got body changes, you can go to settings, then, Face ID and passcode, the enter your passcode to get in, once in, press set up alternate appearance, then you will start set up, when you finish, you can now use Face ID for unlocking phone, downloading apps and the stuffs that normal Face ID does. Or if you meant you wanna turn off stolen device protection, go to settings, Face ID and passcode, enter your passcode, go to stolen device and tap turn off (please note that if you have stolen device always on, you will have to make a security delay (1 hour) and you can make some changes, but if you choose away from familiar locations and your not home, you could go home OR make also a security delay.), then your now free