You wish to close your Heroku Team account
If you have any ongoing charges, be sure downgrade your apps to Free Dynos and delete all add-ons (except the free Heroku Postgres). Alternately, you can just delete your apps. You can do any of this from your Heroku Dashboard or the CLI (as you prefer).
To expedite final payment for any outstanding team balance and close the account quickly, please open a ticket with the billing team and request expedited payment. Once payment has been processed, you can close the team account at any time.