You cannot delete your main domain name within WHM for security reasons. If you wish to remove main domain name and assign same reseller privileges to another domain name already hosted on the same server and under your reseller account, please submit support ticket to support.westnic.net. Please include: main domain name, username and password to WHM.
Please note: there is a one time charge of $25 per entire account. If you have less than 20 domains under WHM account, update is going to be free.