Block all unknown numbers not in my Contacts from calling and messaging on my iPhone I know I can block a number from messaging/calling me, but I can only do this after the event. Is there a way I can stop unknown numbers from messaging/calling before the event, i.e. for numbers that aren't in my Contacts list? My iPhone is running iOS 11.2.6.
Yes, albeit with some trade offs. See this link for some information. If you go to Settings, hit General > Do Not Disturb > Allow Calls From and select Contacts Only. This setting applies to SMS messages as well. Hopefully this is useful.