If you are trying to delete your account, please see How Do I Delete my Account?
In the Plans section of your account settings, click Select Plan next to the subscription option you wish to downgrade to. Your account will automatically downgrade to the selected plan at the end of your payment period and you should receive an email notification to verify.
If you wish to close your plan entirely, select Cancel Plan in the bottom right corner. This option will stop renewals your current subscription at the end of your payment period, at which time you will not be able to go live or create any new content on your account.
If you do not see the option to select a different plan or cancel your subscription, please either contact your account manager or complete this form.