You can cancel your subscription within your account.
First go to the Subscription area of your account by clicking the subscription menu tab
This takes you to the subscription screen that displays your current subscription package.
To cancel your account, click the 'cancel my subscription' link at the bottom of the page.
Then click the green, cancel my account button.
This will close your account and delete your data. You will not be able to retrieve this data once your account is closed.