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. The difference in cost will be pro-rated for the amount of time remaining in your 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.