This is a video on how to change your youtube username from a profile to a page or business name, i shall explain it as well in the comments.
1.First is to go to Your Google + Page.
2.got to settings and got to the bottom and hit Disable Google +.
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3.Go to youtube on that account and hit creator studio.
4.Then hit Reactivate.
5. Under The Two boxes Business or Other Name tab.
6.Then put in your desired name.
7.Reactivate your Google + account.