Go to the "Account" tab and select the Rocketship plan you want. Depending on the number of pages or users you have created, or the amount of storage space you are using, you may not be able to downgrade your plan. (NOTE: you must be the Account Owner to upgrade, downgrade, or cancel your account.)
YES. Go to the "Account" tab to cancel at any time. If you cancel while you are still within your 30-day free trial, then you will not be billed at all.