Yes you can upgrade or down grade the plan at any time.
In order to upgrade your account , you can login at http://webhostingworld.net/billing/clientarea.php
1) Click on Products and services
2) Click on hosting
3) View details
4) Click on edit icon and upgrade package from there
You can upgrade any time; all you have to do is pay the difference in two plans. The upgrade process is instant as soon as the payment is done.
