You can edit the username of your Flirteezy profile easily by yourself. Just open your profile and click "Edit Profile". Fill in a new username and save your profile. The username will be changed, if the desired name is available.
If you changed your username, you must use for the next login your new username. Please note, that other users may not find you anymore, if they are searching for your old username.
If you signed up via Google or Facebook and don't like your username, you can change your visible username as well. Just follow the steps above.