Unfortunately, we can't change usernames for accounts. Doing so can cause serious problems for the account. This includes even a subtle change such as the capitalization of the username.
If you want to get a new username, the best course of action is to deactivate your current account and create a new one. Content, such as uploaded videos, cannot be transferred between two accounts.
If this is the course you'd like to take, then before deactivating your account, you should un-link any external account bindings, such as League of Legends, CS:GO, or other game & social accounts. You can do this in the 'Accounts' tab of the Plays.tv client preferences.
To deactivate your account, Choose 'Edit Profile' on the plays.tv website. There, you can deactivate your account. Input your password to commit to the change.
This will free up your email address to use in your new account.
From there, you can register a new account with the new name that you want.
We wish that there was a way to change usernames. Sorry for any inconvenience.