What is the situation that the main card of Apple mobile phone can be used and the auxiliary card can't be used?

How to switch between primary and secondary cards when sending text messages on Apple mobile phone?

Taking Apple 1 1 and iOS 14.2 systems as examples, the specific methods for switching between the primary and secondary cards when sending short messages by Apple mobile phones are as follows:

1. First, open the Apple phone, click the SMS icon, and open the SMS application;

2. After entering the SMS interface, click the button in the upper right corner to create new information;

3. After entering the mobile phone number of the recipient, the current default SIM card will pop up;

4. Click the "Major Number" button, and major number and minor number options will appear. Just switch to send.

Android phones have supported dual-card dual standby for a long time, but Apple phones have always been single-card single standby, which brings inconvenience to many people who need two cards for work. However, since iPhone xr and iPhone 1 1, Apple also supports dual-card dual standby, and can switch the primary and secondary cards at will when making calls and texting. Click the contact in the address book and enter the details page. You can see the "Main Number" button below the contact name, and click it to switch, which is consistent with the switching method of SMS.

This answer applies to most of Apple's mobile phone models.