Texting between Apple phones is free, why can't some?

Don't pay for data traffic. Social software like WeChat requires both phones to turn on IMessage. SMS must be charged. This has nothing to do with mobile phones ~

There is no charge for imessage. Simply put, it is to send text messages to each other (similar to WeChat). This function is turned on by default when sending. If you don't want to use it, you can go to "Settings" and click "Information" and choose to close iMessage.