I meant to say the caller ID shows numbers from the local area code often. So blocking international numbers might not work.
The signaling data includes the real origin. CID is convenience data provided by the originator. The telcos wouldn’t use it for anything important, like billing.
> The signaling data includes the real origin
Anyone can set up a bunch Asterisk or Freeswitch servers anywhere in the world and use VOIP. How does it know where the "real" origin is.
The origin within the SS7 network. Someone has to pay the bill ;)