Use ''Do Not Disturb'' on your iPhone, iPad, or iPod touch

From the features of the iPhone is " Do Not Disturb"

which make you stop receiving calls at a time you choose , a useful feature in rejecting calls while sleeping or working time in order to even the annoying phone is not for you.

If you don't want to be disturbed at a certain time, you can set a schedule. Tap Settings > Do Not Disturb and turn on Scheduled. Then set a time.