Block all calls from area code unless in Contacts

automation is the preferred option. Many apps are available. I prefer using MacroDroid , since it is free (upto 5 macros) and easy to learn.

You would need two macros for this

First macro would be to set a flag when the call is from an area code

Macro : Area code (name of macro as example)

Trigger:

1. Call incoming → Select number → abc* ( where abc is numeric area code you are interested in and * is wildcard to represent any number . You need to know / experiment here - in my case I needed to type +<2digit country code><2 digit state code>< * wild card > to test with land line telephone

   
   



2. You would need another similar trigger for identifying mobile numbers from that area if / as applicable

   
   

Action: Set Macrodroid Variable → New variable → from area code ( name of flag, it can be anything ) of type Boolean to true

Constraints: Leave blank

In the next macro we reject the call when the twin conditions of calling number is a non contact and from that area code are met

Macro : Reject call (name of macro as example)

Trigger: Call incoming → Select Contact → Non contact

Action:

1. Call reject

   
   

   add constraint to this action by long pressing action

   
   

Macrodroid Variable →from area code = True (Macro only runs in this case, satisfying twin criteria conditions)

2. Set Macrodroid Variable → from area code to false ( initialisation of flag )

Constraints: leave blank

I have only tested with landline available to me and it worked. Logic has been explained and you would need to configure with special attention to area codes of landline / mobile