How to Upgrade the Plesk license.
1. Log in to your Client area account.
2. Go to My Services.
3. Select your Service Addons.
4. Click on Plesk Control Panel.
5. You will see an arrow sign "→" in front of the Plesk licence product you wish to upgrade, click on it.
6. You will get the Upgrade/Downgrade Option.
6. Select the plan you wish to upgrade to with the needed billing cycle and click on continue.
7. It will provide you with the difference amount that needs to be paid. Pay it, and your plan will be upgraded to the next level plan.