Only the organization owner is able to delete your organization. If you're not the owner, contact the current owner to upgrade your role or have them cancel the account.
To completely cancel your account, you will need to cancel payments and delete the organization.
To delete the organization, go to Organizer Dashboard
In the setting menu tab, click on Settings, then click on More Settings
Click Delete in the left-hand column and then confirm.
For help with canceling payments, read this article.