Why can't Apple 4 send text messages?

Apple 4 mobile phone can't send text messages as follows:

1. You can change your mobile phone to see if you can send and receive short messages.

2. If you can send and receive short messages, I suggest you plug the card back into your mobile phone and send yourself a short message to see if you can receive it.

3. If not, I suggest you check whether there is a problem with the sim card;

4. Check whether the number of the SMS center is set correctly;

5. Bring the mobile phone card to the local business hall for testing or replacement.