Manage Bandwidth in WHM
From Lunarpages Web Hosting Wiki
This is how you would manage bandwidth for your accounts using Web Host Manager (WHM). Doing so will give you the ability to lower or raise the bandwidth for any account managed under your WHM account.
The first thing you would need to do is login to WHM. From the front page, click on "Account Functions" and then "Limit Bandwidth Usage". This will take you to the Limit Bandwidth on an Account page.
Select the domain or user name for the account you wish to edit, and then click on the "Limit" button. You are now taken to the Bandwidth Limiter for that specific domain.
In the text box labeled "Bandwidth Limit" type in the new bandwidth limit you wish to assign to this domain. When you are finished, click the "Change" button.