Siri is a built-in “assistant” that enables iOS users of iDevices to speak voice commands in order to operate the device and its apps. Siri voice assistant has many useful commands and features, but some users may wish to disable or turn off Siri for personal reasons.
To Turn Off Siri:
The process to disable Siri is the same for all iOS devices:
1. Open the Settings app and go to “General”
2. Tap on “Siri” and toggle the switch to the right of “Siri” to the OFF position.
3. Confirm by tapping on “Turn Off Siri” and exit.
You can always re-enable Siri by going back to the Siri options and toggling the switch to the ON position.
My personal recommendation is to leave Siri on. You never know when you might need it, specially now a days users are becoming very reliable on voice commands feature.