Apple 1 1 extension can't send text messages.

1, first go to Apple's1/mobile phone desktop and find the green dialing icon below. Click on it;

2. Click Address Book in the bottom menu bar;

3. Then find the contact you want to call and click on it;

4. After entering the contact details page, click the main number under the contact name;

5. Then you can see the primary and secondary number options in your phone, click Switch, and then send a message.