Apple 1 1 SMS can't be sent out. What happened?

Apple 1 1 SMS can't be sent out for the following reasons:

1, confirm that the signal is normal and close the flight mode.

2. Check whether the SIM card status is normal.

3. Check whether the send key is displayed in bright color and clickable.

4. If you can't click Send after entering the text, the "Send" key is still gray.

5. If you send text messages to multiple people and manually enter numbers, please make sure to use line breaks instead of spaces to separate each number.

6. If you can receive or send short messages, you can edit the number of the short message center through internal commands after eliminating the above problems.

Short Message Service (SMS) is a part of Unified Communications Service Plan. Users can directly send or receive text or digital information through mobile phones or other telecommunication terminals. The number of characters that users can receive and send short messages at a time is 160 English, numeric characters or 70 Chinese characters. Short message is a telecommunication service in digital mobile communication system. It is a non-real-time and non-voice data communication service to transmit text or digital short messages through the signaling channel and signaling network of mobile communication system.