It doesn't look like you've purchased any upgrades under this user account. To cancel a domain, the upgrade owner can log in and will see a Cancel and Refund button under Store > My Upgrades, if the domain was purchased less than 48 hours ago.

Canceling a domain after 2 days of purchase means you completely give up ownership of the domain. There is no guarantee the domain will become available to re-register after cancellation.

You are welcome to keep your domain with us and update the name servers to point to another hosting provider by following this guide:
http://en.support.wordpress.com/domains/change-name-servers/

After 60 days from the date of purchase or registrant contact information change, you may also transfer your domain to another registrar by following this guide:
http://en.support.wordpress.com/domains/transfer-domain-registration/

If you would like to completely cancel your ownership of the domain name, please have the upgrade owner log in and reply here to confirm which domain they would like cancelled.

If you need further help, just let us know.