block #

You cannot directly block them before they call however you can Silent Unknown Callers. This will silence the incoming calls that are NOT on your contact list even if you know the person. You can activate this by opening Settings ➔ Phone ➔ Silent Unknown Callers ON. When this is active then you will not hear the unknown number incoming calls BUT the call number will be logged in to your recent calls folder. You can then decide to completely block that number by adding to your call block list - Tap on the information icon next to that number and choose Block this caller at the bottom.

Axel F.

You block them the same as any other number. However most of the time, they are spoofing the number and it won't matter. You can go to Settings>Phone>Silence Unknown Callers, and that will not allow calls from people not in your contacts to ring.