SMS preview interrupts whatever you’re doing when you receive a text message and displays an excerpt of the message on your iPhone’s screen. This can create embarrassing moments when your receive a private text message while showing off your iPhone to your boss, or when a co-worker accidentally glances at your message when you left your iPhone on your desk.
Luckily, it is easy to turn the SMS preview off. Start Settings app and tap on the settings for Messages. Toggle the switch for “Show Preview” to OFF to turn off SMS Preview.