Additional settings-related features and issues within Microsoft Teams Free
Hello, thanks for reaching out.
To remove your old Teams Free account from your phone, open the app and go to your profile or account list. Tap the old account and choose Sign out. Then go to your phone’s Settings, find Accounts, and delete that Microsoft account from the device.
Once it is removed, the app will stop asking for its password. You cannot delete or merge a Teams Free account from a past employer directly in the app, so signing out and removing it from your device is the way to stop it.