If you create an organization, you only have the option to remove verified domains and linked sites functionality, but do not have the option to remove the created organization. You are able to rename the organization, but not remove it completely.
Allow organization administrators to delete organization as this can make the functionality confusing.
You can cancel the subscription from Billing. Refer to the document Unsubscribe from Atlassian Access for more details.
It is also possible to transfer an organization into another organization, and thereby "delete" the original organization.