Within Teamwork Chat you can quickly edit your chat handle which other users will use to create a chat with you or directly notify you within a group chat.
To edit this, click on the cog icon in the bottom left corner, right of your profile photo. From here you'll be brought to your profile settings which you'll find your chat handle.
By default, the handle that will be chosen for you is your first name however if another user already has a handle with your first name, then yours will default to your first name and first letter of your surname.
For more information on using handles see: Notifying users when posting a message