How does Apple's mobile phone trumpet receive information?

Step 1: Open the information function of iPhone 1 1 and click the new information icon in the upper right corner.

Step 2: Enter the recipient number, or press the+key to select a contact.

Step 3: If the recipient is not in the address book, the default SIM card will pop up when editing the short message; If the recipient is in the address book, the default SIM card will pop up after selecting the recipient.

Step 4: Click the default SIM card, and two options will pop up: primary number and secondary number.

Step 5: Select the secondary number.