Why can't realmegtneo3' s secondary card receive Unicom's customer service SMS?

The main card is not supported. In this case, if it is impossible to query the secondary card in the online business hall, it is not excluded that the local Unicom does not support the use of the primary card to query the usage of the secondary card in the online business hall, resulting in the inability of the mobile phone to send and receive short messages. You can try to restart or replace the mobile phone for testing.