how to stop iphone change from speaker to audio

I have an iPhone 12 Pro.  

Bluetooth is OFF and is never on.

I have removed facetime. 

I do not have linked calls set up. I never have had linked calls on this phone. 

The speaker option changes to audio every few days. I turn off and on the phone and

this resets back to defaulting to speaker (no other options).

I want to permanently stop my phone changing from speaker to audio.

I am not connected to iCloud. 

I reset my phone, and for several days when I go to make a call (or receive) it

shows the option as speaker. 

After several days the speaker icon changes to audio and shows 3 options (speaker,

iPhone and iPad). 

My iPad has never been linked to this iPhone and does not have Bluetooth on.

I have gone through the articles that say about unlinking a device but no where

are these two devices linked (That I can find).

I only want the speaker option, and I don't want to have to reset every few days.

My previous iPhone (X) did not do this.