Right, I see that you previously received a refund but did not downgrade your plan at that time. As a result of not cancelling the plan or deleting the team, you got a new invoice for the new billing cycle. That new invoice seems to be unpaid based on the screenshot you shared.
The warning on your screenshot clearly states, "You have unresolved outstanding balances. Please visit your team's invoices to resolve outstanding balances before deleting your team."
As mentioned before, I do not have the ability to delete the team for you. You'll need to sort out your outstanding invoice before you can delete the account. If you still have trouble and need additional guidance, please open a support case so the specialist team can help with your billing issue.