Originally Posted by
D582
Not true - you can choose the setting.
In General, Settings, Do Not Disturb, Silence -> Always
OP, if you change that setting, and also Allow Calls From - > No One, and Repeated Calls -> Off, that should totally prevent interruptions
Apple disagrees with your statement
"With Do Not Disturb, you can silence calls, alerts, and notifications that you get
while your device is locked. You can also schedule Do Not Disturb and allow calls from certain people."
https://support.apple.com/en-us/ht204321