Removed guest from Teams but guest still able to see the Organization

My experience is that it can take a whole before the Teams app "catches up", often due to locally cached content. You may want to clear the local Teams cache from %appdata%\Microsoft\Teams, which should force Teams to retrieve all details again from the cloud. You can often validate such cache issues by checking the web version of Teams to verify if it has the same issue as the local client, and I expect that this user will not see the organization when visiting https://teams.microsoft.com.