TTY mode is a feature of mobile phones that stands for either 'teletypewriter' or 'text telephone. ' A teletypewriter is a device designed for the hearing impaired or those who have difficulty speaking. It translates audio signals into words and displays them for the person to see.
TTY may be unavailable or unreliable when using Wi-Fi Calling or on a Voice over LTE call. If TTY services are needed (for an emergency call or otherwise), GCI recommends disabling the Wi-Fi Calling feature and VoLTE on your Device and continue using your existing TTY services on the GCI wireless network.