In the billing section, you can find information about your current pricing plan and the usage in the current month. You may also upgrade your plan as well as manage your subscription once you choose a dedicated plan. See the following pages for details.
Please note that if your root user has been created under a higher level of the account hierarchy by a partner, you will see the 'Usage' tab instead of the 'Billing' tab. In this case, you will not be able to change the billing plan.