How do you change your Minecraft player name? [duplicate]
Solution 1:
Users who have a Mojang account (you sign in with your email) can change their username for free at account.mojang.com/me by clicking the (Change) link next to your profile name.
A user who changes their username cannot change it again for 30 days.
Source: https://help.mojang.com/customer/portal/articles/928638-minecraft-usernames