How to block an area code on an iPhone
A recurring question in this Community which I struggled with myself is: How do I block all calls from a specific area code?
What I finally figured out was to create a new contact in my Contact list, with nothing but:
+1 (xxx), the xxx being the problematic area code.
Then, when that contact is saved, open it, scroll to the bottom, and click on "Block this Caller", which is in red.
Open your Blocked numbers list in Settings and verify it's there.
iPhone 11, iOS 16