with regard to changes to the game's NickName, it can be changed through a report to Technical Support, if you clearly report a link/association with your physical person (e.g. first and last name), report sensitive data or otherwise be in violation of the Privacy Statement, Terms of Use and/or other applicable regulations.

This is the main rule of the game. While there is an exception for system-generated nicknames (as long as it is the first request and has not had any other nickname changes):

your current nickname is the one automatically generated by the system, objectively talking you need to contact Technical Support in order to get this chance. 

Contact our Customer Support, they will evaluate the possibility in a better way. 

Regards,

KoD