Change Subscription Plan
If you paid with a credit card you can easily change to a different subscription plan if you wish. Just select a different subscription, and it will do a prorated conversion to it. So if you have an annual membership, but decide to go to a monthly, it will refund the remaining amount of the annual membership. Then it would charge you for a new subscription and extend the membership to the new expiration date based off that new subscription.
If you paid with PayPal and you wish to change to a different subscription plan, cancel your subscription before the expiration date. After your subscription expires you can establish a new subscription plan by going to the subscription page.