All our shared seedbox and monster seedbox can be upgraded to a higher package anytime from our manager. You will only need to pay the difference between your current account and the account which you would like to upgrade to. We will start the upgrade at the before the renew of your current plan.
In such a situation you will get an email with the information when we started and finished your upgrade.
The downgrade option is not available with shared and storage seedboxes at all, to do this you need to order a new account and cancel the old one.