If you would like to upgrade, switch  or downgrade your subscription then got to My Account from the Main Menu

Step 2. Click on “My Subscriptions”

Step 3:  Click on your Subscription Number and scroll down until you see “Action”

Step 4: Click on Upgrade or switch Subscription or resubscribe

You account will be prorated per your membership plan

You can also hover over “SHOP” on the main menu and click on “Membership Options”.  Check the membership box that you want to switch to.  This system should switch and prorate your price.