How do I block international calls at all?

A. 1

http://blog.naver.com/service_ace/10177828019
You can refer to the contents here.

Gentleman 9 years ago 0

OK

A. 2

You can enter the carrier's customer center and apply for an international call rejection service.
If an international call starts with 00x (International Phone Identification Number), it will automatically be blocked and you will be notified by text that an international call has been made.

Gentleman 9 years ago 0

OK