Do I have to re-register a new Facebook account to change my facebook.com/USERNAME?
Or are there any ways to change it?
You can only change your Facebook username once. If you have already changed it then there is no way to change it again. You would have to setup a new account and claim a new username that way.
The option to change your username is in
Account Settings >
Username. If that option is not available then you cannot change your username.
How do I change my username?
You can change your username from the Settings tab of the Account Settings page. Scroll down to "Username" and click "change." Then follow the on-screen directions. Keep in mind you will only be able to change your username once.
You can only change your Facebook username once. It seems that you have done it already.
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