Yes, you can alter your cPanel account username. Please open a support ticket, if you want to change the cPanel username.
Though please notice that your username is limited to 8 characters length.
And also we should notify you about viable issues which may happen after such a move:
- If you own a website which is using a database, the site's MySQL configuration should be modified accordingly to the new account username. Usually, it is done by altering the configuration file;
- The new cPanel username should be the equal length or shorter in order to restrict MySQL from truncating the account's database names and database usernames;
- Also, an email account which has the same username as cPanel has cannot be created