If you want your callsign changed you can do it self service on this discourse forum, click top right on your image, click on Profile, then Preferences, then select the edit pencil next to your username.
For the main WOTA site you’ll need to message me or add a note to the forum, that requires a direct database update for the login. As part of that process I can migrate your log entries for which there is an admin process.
Mark.