What Does Do Not Disturb Do on Iphone 7

Do Not Disturb is an easy way to silence iPhone, whether you’re going to dinner or to sleep.
It keeps calls and alerts from making any sounds or lighting up the screen.

Do Not Disturb 
Turn on Do Not DisturbSwipe up from the bottom edge of the screen to open Control Center, then tap iphone  Do Not Disturb simbol
When Do Not Disturb is on iphone  Do Not Disturb simbol appears in the status bar.

Alarms still sound, even when Do Not Disturb is on. To make sure iPhone stays silent, turn it off.

Configure Do Not Disturb.
Go to Settings > Do Not Disturb.

You can schedule quiet hours, allow calls from your Favorites or groups of contacts, and allow repeated calls to ring through for those emergency situations. You can also set whether Do Not Disturb silences iPhone only when it’s locked, or even when it’s unlocked.

When pressing the volume button, a “turn off do not disturb” mode dialog appeared.