You can change your user name on your own in the account settings.
This is how it works
- Open your browser and log in.
- Click on the gear wheel and then select Account.
- Click on Change in the section User name .
- Choose your new user name and click on Change.
- Open the app on your device.
- Open the main section Profile in the app.
- Tap on Settings.
- Tap on Change user name.
- Enter your new user name and afterwards click on Finished.