I'm sorry for the inconvenience.
Unfortunately, you cannot change your username as of now due to the topic being closed, as stated above.
If you'd like to change your username, you'd have to wait until the Admins open the topic once again. The topic can be found HERE for future reference.
Unfortunately i cannot give you an estimated time for when changing name will be again available, but you can stay tuned in #announcements of our OFFICIAL PRO DISCORD for further announcements about that and other updates.
I hope the information given provided some clarification, please let me know if something is unclear and if you have any further questions.
Have a wonderful day!