The SMS function of Apple 13 secondary card cannot be activated.

After the dual card is set, by default, the main number is usually used to send text messages. If you want to use the secondary card to send text messages, you need to manually switch the primary and secondary cards. When you get back to the phone desktop, find and click the dial icon. Click Address Book in the bottom menu bar. Then find the contact you want to call and click it. After entering the contact details page, click the main number under the contact name, and then we can see the main number and secondary number options in the mobile phone, click the secondary number and select Finish, and then select SMS to send to the contact.