If you'd like to cancel your Business Catalyst account please follow these steps after logging into your Business Catalyst Console:
Select Site Settings > Site Management, and then click Delete Site.
Enter your Creative Cloud email address and password, and then click Continue.
Click Delete Site.
Please take note that there is no undo for this operation. Your site and everything inside it will immediately be irretrievably deleted. Please ensure you've exported important data such as CRM records and mailing list subscribers.