If you'd like to change your membership plan (i.e., change from the Quarterly Plan to the Semiannual or Annual Plan), just go to the Membership Plans page and purchase the plan that you'd like, and then cancel your previous plan on your ClickBank Customer Account. Access to your previous plan will continue to the end of its term, but will not be renewed or rebilled.
For detailed instructions on canceling your previous plan, go here.
You will receive a notification email prior to rebilling/renewing your existing plan(s), so we recommend you wait until receiving that before you change your membership plan(s).