How to use imessage to send messages between Apple phones for free?

If there is no SMS fee for texting between Apple mobile phones, only a small amount of traffic will be deducted.

Sending method:

Open the message and click the Edit Message button in the upper right corner of the screen to add the other party's mobile phone number to the recipient. At this point, if the other party is an Apple phone, you can see the words "new iMessage" at the top of the screen. Write the information content before sending it.