Minecraft and xbox: Gamertag?

You can change your gamer day after a month. And I wanted to ask on which side you do it and whether you have to change it again on the same device?

https://account.mojang.com/...ojang.com/

have to log in and can then change it

You can change that on the official Xbox page or on the official Microsoft page.

Microsoft.com

Xbox.com

And no, you don't have to change it on the same device.

Oh and you can also change your name with the official Xbox app