The mobile phone shows that the short message has been sent, but the other party cannot receive it.

There is generally a "SMS center number" in the SMS settings, which is the number of the SMS transfer station. Generally, the number of SMS center in each province is the same and unique. After the mobile phone is connected to the Internet, the system will automatically select this number. However, if someone accidentally changes this number, then there will be the situation that your mother can't send text messages! It is recommended to check whether there is any problem. If not, then check whether it is a mobile phone problem. Since you and your dad can send text messages smoothly, it means that there is no problem with local mobile communication, but the problem is still your mother's mobile phone!