Upgrades and downgrades are both handled through the account management page that is available when you log in to GraphFree.
Upgrading Your Subscription
You may upgrade your account level from Standard to Boost at any time.
When you upgrade to Boost, it starts a new 12-month subscription. Any time you have remaining on your standard subscription will be refunded and applied as a discount to the new Boost subscription.
Downgrading Your Subscription
You may downgrade your subscription from Boost to Standard at any time. Depending on the timing of your request, the downgrade may take effect immediately, or you may receive the benefits of the Boost subscription until you have exhausted the benefits you have already paid for.