How to set up Apple's SMS if it can't be sent out?

The setting method of this situation is as follows:

1. Check your network connection: Tap the Messages application, tap Retry, and if you still can't send the message, tap Send via SMS.

2. Restart the phone: press the phone power button lightly, slide it off, and then turn it on again.

3. Restore network settings: enter the settings, general and restore interface, and select Restore network settings.

4. Turn on the SMS sending function: enter Settings, Information, and send by SMS to turn on this function.

5. Check whether the phone number is set to send and receive information: Go to Setting Information Sending and Receiving and check whether the phone number is set to send and receive information.