In the unlikely event that you need to prevent someone from accessing your team after removing them, you can regenerate the team code with the steps below.
Start in the Team tab -> click Team settings and then "Generate new team code".
You can also Lock your team from new members and choose to unlock it whenever you expect a new member. Heja will encourage this individual to reach out to the coach or admin of this team. This way you have more control over who joins the team.