How can I disable voice dialing when the iPhone is locked?
Sometimes it's handy to voice dial when your iPhone is locked with a passcode. You can skip all of the steps required to unlock the phone and call by simply holding the home button until Voice Control prompts you for a command.
This also leaves your contacts open to anyone who finds the iPhone but doesn't know your passcode. To make sure the iPhone will only voice dial when unlocked, follow these steps:
1. Navigate to Settings -> General -> Passcode Lock
2. Enter your passcode
3. Select Voice Dial -> OFF