Forum Discussion
Cannot remove a Guest from a Channel or a Team
Managing the channel and attempting to remove guest members by pushing the X simply results in the X returning after a second or two and the guest member remains.
That isn't how it is supposed to work so that is frustrating. If you continue to see this, please go to answers.microsoft.com so they can help you troubleshoot.
If you are an admin, you can remove them from AD, too - instructions for doing that here: https://www.wavecoreit.com/blog/teams/removing-microsoft-teams-guess-access-user-team-part-2/