What happened to the failure of sending SMS on Apple's mobile phone?

The failure of sending SMS on Apple's mobile phone is often due to the failure of network settings, which can be solved by restoring network settings in Settings.

Take Apple 7 as an example, the specific operation is as follows:

1, click "Settings".

2. Drop down and click General.

3. Pull down, find "Restore" and open it.

4. Click Restore Network Settings.

5. At this point, you need to enter a password to pass the verification. ?

6. After the password is verified successfully, select "Restore Network Settings" from the pop-up options.