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.

Solution 1:

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.

Solution 2:

You can create a contacts group and add all (or desired) contacts to that group.

On your iPhone, enable Do Not Disturb. Go to Settings app → Do Not Disturb and select the group All Contacts from within Allow Calls From section under Do Not Disturb.

You can also create a Contacts group to selectively segregate contacts. To create a contacts group, refer to the Apple Support article, iCloud: Create a group and add contacts to it.

Update: Apparently an easier approach is to select All Contacts in the aforementioned step, instead of creating a group and selecting it. All Contacts option is available by default.