If you have a paid subscription you can cancel your subscription by:
Go to Settings. This is at the bottom of the navigation
Choose the Billing tab
Click the "Manage Billing" button to go to your billing portal then choose Cancel
This will cancel your subscription and downgrade your account to the free plan where you'll still retain access to your data.
To delete your business entirely:
Go to Settings
Click the "Delete" button. This is in the first "Business" tab.
Confirm deletion
This will immediately and permanently delete your account, it cannot be undone.