How do I permanently disable the "Enable dictation" iPhone feature?

The feature Dictation can be toggled off/on in Settings..

also from Safari and SIRI as well.

• Improve Siri and Dictation & Privacy - Apple Support

//www.apple.com/legal/privacy/data/en/improve-siri-dictation/

[Apple] › legal › privacy › data › en › improve-siri-dictation

"You can disable Siri and Dictation by going to Settings > General > Keyboard and tapping to turn off Enable Dictation.

Then, go to Settings > Siri & Search and tap to turn off "Listen for 'Hey Siri'" and "Press Side Button for Siri" (or "Press Home for Siri" if your iPhone has a Home button). Siri Data associated with the random ..."

Other areas in Apple Support also refer to how to 'turn on/off' features.

The above Apple Legal document suggests how, why this works too.

• How to enable, use, and disable dictation on iPhone and iPad | imore

/www.imore.com/how-enable-use-and-disable-dictation-iphone-and-ipad

• How to Turn Siri Off on an iPhone or iPad | lifewire

https://www.lifewire.com/how-to-turn-off-siri-4173769

"Just because Siri exists doesn't mean you have to use it"

PS:

• Use Voice Control to interact with iPhone - Apple Support

•Dictate text on iPhone - Apple Support

•iPhone User Guide - Apple Support

• iPhone User Guide (Table of Contents) - Apple Support

//support.apple.com/guide/iphone/toc

These would have more details across a wider range.

With microphone button, you have to be careful it's

either is disengaged or opted out; if that's a problem.

"..using certain features and services that transfer data, such as

Siri and Messages ~ could result in charges to your data plan.."