Hello I want to change my username Williamhanwha, to WilliamKim. I accidentally typed in my actual 'nickname' and didn't expected to be marked at the copyright and unchangeable. I will appreciate it if you modify the name.
The Copyright bar shows what you have entered as Photographer name, and that can be changed. Forum username can't be changed though Go here, and scroll down to photographer name:
If you're talking about the copyright bar of uploaded photos, it will show the name you provided as photographer name in your settings (https://www.airliners.net/user/account/settings). Not the username that you use for the site.