Apple 4s sets the number of SMS center.

IPhone phone can't send SMS for troubleshooting;

1. Make sure 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 on and clickable.

4. If you can't click Send after entering the text, the "Send" key is still gray. Please turn off "Show Subject Bar" in Settings SMS.

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 not send short messages, you can edit the number of the short message center through the internal command after eliminating the above problems:

Set SMS center number: dial *5005*7672*+86 SMS center number # with iPhone;

Delete SMS center number: dial ##5005*7672# with iPhone.

Inquire about the set SMS center number: dial *#5005*7672# with iPhone.

When using the internal command, first use the delete command, and then set the SMS center number.