Apple's 5S mobile phone can make calls, but it can't send and receive text messages. What should I do if I display "undelivered" when sending a text message?

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

2. Check whether the SIM card status is normal, replace the SIM card and restart the phone.

3. Maybe the number of SMS center is not set. It is suggested to call the operator's customer service: Mobile 10086, Unicom 100 10, Telecom 10000.

4. After eliminating the above problems, you can edit the number of SMS center through internal commands:

(1) Set SMS center number: dial *5005*7672*+86 SMS center number # with iPhone.

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

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

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