Shared
Unfortunately, you may not change the user name associated with your control panel. Once it is set, there are vital components using that name. Some of those settings are used by your web site, and are not controlled by Deezon.
Reseller and SEO
You may change the user names for any accounts you create by going to WHM and clicking the Modify Account link (read more in the related article). However, you cannot change the user name you picked during sign up.
There must be a way to change my signup username.
The only solution Deezon can offer is to terminate the hosting account, and then recreate it with the desired user name. WARNING: Accepting this solution will erase all web site content, emails, databases, and everything you have done on the server so far.
VPS and Dedicated
You may change the user names for any accounts you create by going to WHM and clicking the Modify Account link (read more in the related article). However, you cannot change the user name provided by Deezon; Linux is always root, and Windows is always admin.