You can now fully manage your account plan or cancel your AvConnect account using your personal web portal. Log in to avconnect.net and visit the "account" link at the top. Click the "plan" menu option to select a new plan or cancel your account.
Please keep in mind that you can select the Logbook Lite plan, which is always free of charge. This is a nice electronic logbook with some perks that you will enjoy at no cost.