Log in to your Seller Assistant account and go to the subscriptions page, where you can see your current subscription plan.
To upgrade your subscription plan, click the “Update Subscription” button.
After clicking the “Update Subscription” button, you will be redirected to Plans page.
Choose another Subscription Plan and click "Select" button.
Wait for the plan to upgrade. In meantime, the payment system will automatically recalculate the tariff and withdraw the payment from the linked payment card.
If the payment is successful, in your personal account you will see a new subscription plan.
You might also find article "Add-ons in Seller Assistant" useful.