youtube
I registered as, say John Doe, and then later on, created a YouTube presence with a name such as "Cool Gaming Channel" and a channel also with that name.
Yet after I published a video, and I viewed it, the name displayed is "John Doe" and I couldn't find a way to change it. How can it be changed to "Cool Gaming Channel"?
No, unless the owner wants to do it there is no way that you could claim another username. just find another name, for example mybusinessofficial or anything else.
It may be helpful to read the YouTube's username trademark policy.
Problem is, they're probably not infringing your trademark, as you may know, just using a name doesn't infringe a trademark, what is important is "how" they use it. that said, if they even try to upload any content, similar to yours, which imply that their channel is connected with your brand, then you may use YouTube Trademark Complaint Form to take down their content, their account or assign it to yourself.
Attack this from the outside.
Use Google's filtering capabilities.
For example, let's say I wanted to search for videos by user "MyAbridged" posted in August, 2012.
I search for myabridged site:youtube.com to get videos by that user.
Then click Search Tools and you will see Any Time come up as an option.
Finally, click Any Time, choose Custom Range, and select the time frame you want to restrict your search to.
Complete your search and you now have all the videos posted by that user in that time frame.
Example search: myabridged site:youtube.com between Aug 1, 2012 and Aug 31, 2012
Note that this search technically searches for any pages within Youtube that mention the name "MyAbridged" anywhere in the page, so it will actually return back more than just their videos, but it will get you where you need to go
Best Answer
from: https://support.google.com/youtube/answer/2657964?co=GENIE.Platform%3DDesktop&hl=en