Domain names automatically renew every year, if you do not wish for your domain to be renewed at it's expiration date, please follow these steps:
Log into the customer's portal.
Click on 'Domains' then on 'My Domains'.
Find the domain you wish not to renew and click the green "Active" button.
Click on the 'Auto Renew' button at the left side box called 'Manage'.
Click the ‘Disable Auto Renew’ button.