Signed in with correct MS account -- how 2 remove wrong one

Create a new LOCAL account and give it administrator access. Log in to the new local account. Copy any data files you want to keep out of the old user accounts. Delete the old user accounts from the computer completely. Reboot for good measure, but probably not needed. Then create your new desired account, make it an administrator. Log into it, copy data files if you need to and then delete the temporary local account you created.

Also, a little hint. If you create a local user account first, you can control what name your user folder gets. For example, I also create a local user, John, first, because that is what I want my user folder to be named. Then I just add my Microsoft account login to it.