Unfortunately, the username for cPanel accounts can't be changed as it's heavily included in the file paths for your website.  Changing your username would likely break your cPanel account and so you would not be able to do this.  You can however change your password at any time.

If you have a Cloud account. please contact support by Chat or Support Ticket and we can modify your username upon verification of account ownership.  

You can also add a completely new user for your account under your cloud control panel by: 

1. First select Manage Account.
2. Select the Create Login tab.
3. Enter a new Username, Password and select a Role for the new account.