How to turn off virtual assistant when phone screen is locked?

[AC Question]

Turned on the virtual assistant and now the screen is locked and asking for a password. However you can't type in any letters and I can't shut the phone off. It will restart and go right back to locked screen asking for password

 

[B. Diddy]

Welcome to Android Central! Which phone? Are you saying the keyboard doesn't come up when you tap the password entry field?