Iphone uses imessage to send text messages, and it can't be received without traffic.

You can receive traffic even if it is not open. The solution is as follows:

1. First unlock the phone and enter the main interface. Then on the main screen of the mobile phone, find the setting icon and click to enter the setting option.

2. Enter the settings list, and then slide up in the list interface until you see the SMS function.

3. Click the SMS function, enter the submenu below, find the imessage option, click the button behind imessage, and it will turn green and open.

4. After successful activation, enter the SMS interface, and the words imessage in gray will appear in the text input box.

Send a message to your mobile phone to see if the dialog box will turn blue, so you don't have to pay for sending a message.