To set options for Siri, go to Settings > General > Siri. Options include:

• Turning Siri on or off
• Language
• Voice gender (may not be available in all areas)
• Voice feedback
• My Info card
• Raise to speak

Prevent access to Siri when iPhone is locked. Go to Settings > General > Touch ID & Passcode (iPhone 5s) or Settings > General > Passcode Lock (other models). You can also disable Siri by turning on restrictions.