An order upgrade is done in these steps:
Auto-recharges are processed by payment processors – 2Checkout, Gate2Shop or PayPal. Auto-recharges are tied with a Brosix order. Because the upgrade cancels the old order, we should create a new auto-recharge with the payment processors. To protect our customers from unauthorized charges, we ask them to manually set up their Auto-recharge. This is as simple as just following a link to make a payment.
When your new order is going to expire you will receive a reminder e-mail with a link. Just open the link in your web browser and follow the instructions to make a payment for the next billing cycle and set up a new auto-recharge.