User name change

Hello, yes if you want a name change you have to pay for it!!

Go over to your name click on profile and then ganertag boom. If u have used your free one then you will have to pay 10 dollers

Try this link https://beta.support.xbox.com/help/account-profile/profile/change-xbox-live-gamertag

Hi,

If you are looking to change your gamertag, you can do that online or on your console.

Online:

1. Sign in to
   https://social.xbox.com/changegamertag with the Microsoft account email address and password associated with your gamertag.
   
2. Enter your own gamertag or select one of the suggested ones:
   • If you’re making your own, type in the new gamertag, and then select
     Check Availability. If you receive a message that the gamertag is already taken, you’ll need to create another one.
   • If you want to use one of the gamertags that Xbox provides, but you don’t like any of the suggestions, select
     Refresh to see additional gamertag suggestions.
3. Once you find an available gamertag, select Claim it.
   

On Xbox One:

1. Press the Xbox button
   
   
   to open the guide.
2. Select your gamerpic in the upper-left corner, and then press the
   A buttonon your controller.
3. Select My profile > Customize profile, and then select your current gamertag.
4. Under Choose your new gamertag, create your own gamertag or select one of the suggested ones:
   
   • If you’re making your own, type in the new gamertag, and then press the
     A buttonon your controller. If you receive a “That name isn’t available. Try a different one” message, that means you’ll need to create another one.
     
   • If you want to use one of the gamertags that Xbox provides, but you don’t like any of the suggestions, select
     More suggestions to see additional gamertag suggestions.
     
5. Confirm that you want to change your gamertag.

After you confirm your new gamertag, the change is reflected across Xbox, and if there is an additional cost, the payment option associated with your Microsoft account is charged. You don't need to tell your friends that you've changed your gamertag—their
friends lists will be updated automatically.

You can find more information here
https://beta.support.xbox.com/help/account-profile/profile/change-xbox-live-gamertag

when you say "username" do you mean Gamertag?