If you see the TTY icon, which looks like a telephone receiver over a series of white dots , on the status bar at the top of your iPhone, the TTY feature is turned on. This feature, which is designed so hearing-impaired and speech-impaired people can conduct phone calls, can be turned off in the iPhone Settings.

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Step 1

Tap on the Settings icon on the home screen.
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Step 2

Scroll down the Settings screen and tap Phone.
Step 3

Find the TTY button and slide it to the Off Position.
About TTY
TTY stands for <ahref="http: 2009="" fatwalr.us="" 09="" tty-iphone-icon="" "=""> </ahref="http:>teletype. A separate TTY device -- which typically incorporates a keyboard and a screen -- is connected to the phones on both ends of a call for the parties to communicate. A TTY call differs from text messaging in that it is designed to be interactive back-and-forth communication just like a regular voice call. As one participant types a remark, it appears on the TTY device of the recipient, who can then type a response. Think of it as a phone call that is conducted by text.
TTY devices can be used both on landlines and on cell phones -- analog or digital. An adapter connects the iPhone to a TTY device.