To terminate an account in WHM :
>>Login to your WHM Control Panel and click the "Terminate Account" setting on the lefthand side of the screen under the heading, "Account Functions ."
>>This page will show you two boxes :
One lists all current domains and the other lists all current users. If you wish to remove a domain its entirity, select it from the box on the left and then click the the button labeled as Terminate.
If you only wish to remove a user account, select the account from the box on the right side of the page. Once you have done so, click the button labeled as Terminate.
Once you have performed either one of these you will be taken to a page telling you the account has been terminated