Unfortunately we can't change your Username. It's a technical thing that has to do with databases, and syncing accounts.
Please note that no-one else except the admin staff of The Online Dog Trainer can see this name.
If it's a real problem, I can suggest you cancel while you're still on the trial, and sign up again using a different name.
You can change your Name in our system (visible only to admin staff in the backend and used in things like the personalised emails we send you). To do this please login and navigate to the My Account page (inside Resources section). Then scroll down and you'll see a form to change your name.
Forum Display Name:
The forum is a public community, and everyone can see your display name in the forum. The great news is you can change this. So if you want a different name to be visible inside the forum, please login and click on this link: https://members.theonlinedogtrainer.com/how-to-change-your-forum-details/
Login here: https://members.theonlinedogtrainer.com/login
Hoping that helps!