Only users with the Full Account permission can can cancel the account.
You can cancel your account from within the software. Simply sign in and visit the account settings page.
Next, click on the "Actions" drop down and select "Cancel Subscription." A popup will appear giving you information and a questionnaire regarding your cancellation. Click on "Confirm Cancellation" after answering the questions complete cancelling your account.
Note: you will continue to have access to the system until your next renewal at which point the account will be closed. The status of the subscription will change to Pending Cancellation in the meantime until that time.