These instructions show how to disable Siri on the iPhone. The instructions below are written based on the current iPhone operating system as of June 2019. If when you read this your iPhone is newer or older, the screens may appear differently for you.
STEP #1 – From Settings Tap Siri & Search
From the Settings menu in your iPhone, tap Siri & Search.
STEP #2 – In Siri & Search Disable Siri
Use the sliders to stop Siri from listening, or disable by turning off the side button option for Siri.
STEP #3 – Confirm
Tap on Turn Off Siri to disable Siri as shown below.