Unfortunately, there is no way to change your @ username as of today 😕
However, you can always create a new account with a different email address in the meantime.
It's possible this could change in the future as we would like to make this possible, but we don't yet have a timeline. This is one of the hard parts or tradeoffs of building in a blockchain-based paradigm that we are working to improve over time.
If, and when, this changes, we will be sure to let the community know. We'd love if it was easy for everyone to change their usernames!