How to choose primary and secondary numbers for iphone SMS?

Iphone sends SMS to select primary and secondary numbers.

1. Take Apple X max's 14 system as an example, and click the information to enter, as shown in the following figure:

2. Enter the information interface and click New, as shown in the figure below:

3. Enter the new interface and click the recipient, as shown in the figure below:

4. Enter the recipient number or add an address book, as shown in the figure below:

5. After adding the recipient, the default mobile phone card name will appear. Click on the mobile phone card, as shown in the figure below:

6. The option of two cards appears, and switch to the card to be used, as shown in the figure below:

7. If the handover is successful, enter a short message and click Send, as shown in the figure below: