Upgrade or Downgrade a cPanel Account
This article covers how to Upgrade Downgrade Package of an Account.
1) Log in to your WHM: SERVER-IP/WHM.
2) Type "Upgrade/Downgrade an Account" in the top left search box.
3) Select Domain with the box on the left.
4) Click “Modify”.
5) This will bring up a new page, select the new package for the account.
6) Click “Upgrade/Downgrade”.