Is there a way to change the username I use when entering server?

[Tru3thful]

You could check some details here on the relevant section on the Account Management Guide:

@wiki

Renaming Your Account

You can also request an account rename. However, it will only be acknowledged when necessary. For example, if you don’t like your account name, if you want to change it just for fun, or something else; your account rename request will not be acknowledged.