Cell phone is missing. How do I change password when my trusted device is no longer available?

Hav you tried Account Recovery?

The Recovery Process is an automated process and the length of time it takes can vary a lot. Apple ID Support can only answer your questions. They can't intervene in or speed up the process. The article below has some suggestions to shorten the time the process takes.

Apple ID - Recover your Apple ID with two-factor authentication account recovery.   *

See if anything here helps.  If necessary, you can use account recovery as explained in the link at bottom of the article.

Verification code - how to get one and sign in with two-factor authentication.   *

Can you report the cell phone as lost/stolen through an icloud account using a web browser?

I am not very familiar with the setup of corporate iPhones using a "trusted device".

Good luck.