How does Apple's mobile phone hack each other's phone calls and text messages?

System: IOS 15. 1

Take iPhone 13 as an example. Hacking the other party's phone and text messages can enter the phone address book, and select friends to block contacts. It is divided into three steps, and the specific steps are as follows: 1 Enter the phone address book and select friends.

Click to block this call number.

3 Choose to block contacts