How to switch between Apple's dual cards and send text messages?

Apple's dual-card switching method for sending SMS is as follows:

Tools/materials: iPhone 1 1, iOS 15, local settings.

1. Open the SMS editing dialog box and click the sender number above.

2. Click the calling number to switch the main and secondary cards.

3. If it is a new message, just enter the recipient information and click the phone card button to switch.