Deleting a team
You can delete a team by going to your team's page in Trello, clicking on the "Settings" tab and then clicking the "Delete this team" link. You must be an admin to delete the team.
Deleting a team is permanent and there is no undo. Boards within the team won’t be deleted. Instead, your boards in this team will sit on your account without a team. You will need to place that board on a different team before you can invite other members to join the Board.
If the team still has an active Business Class subscription, then you will need to cancel the subscription first before being able to delete the team.