How to send text messages on Apple's mobile phone secondary card?

First open the information application, and click New Information in the upper right corner, as shown in the figure below:

Secondly, enter the mobile phone number of the recipient, as shown in the following figure:

3. Select the number stored in the address book and the current default SIM card will pop up directly, as shown in the following figure:

4. Click the default SIM card, and the minor number and major number will pop up at the bottom of the screen, as shown in the figure below:

5. Select the secondary number, and then switch to the secondary number to send SMS.