How to set up a refusal to let the other party know that you are abroad?

Set up the incoming call firewall. Smartphones can download a mobile phone call firewall. There is a blacklist in the arson wall, which means the same as the rejection of the above call. Just like the blacklist in QQ, set the number of overseas calls as a blacklist, or set the answering mode on the firewall to only accept business cards, so that overseas calls cannot be dialed.