You can now upgrade and add features such as additional numbers to your subscription at any time using the Upgrade page of your web portal, which can be found under the Account tab.
You can use this page to upgrade your subscription to a different plan or add the International Calling Feature or space for additional numbers on your account.
Your billing page can not be used to downgrade services at this time. If you need to downgrade service and receive any sort of refund you must still contact support at email@example.com. Thank you!