There is a mobile phone number C, which is no longer used. Then use the other two mobile phone numbers A and B to send a text message to C. A can't send it, but B can?

This is usually caused by the setting of mobile phone card or mobile phone. Some mobile phone numbers or mobile phones will return the notification of successful sending when sending short messages, and only display the success of sending short messages. If it is not received, you will be prompted that it cannot be sent. Reverse the order of ab card to know whether it is card setting or mobile phone setting.