How can a text message sent by a mobile phone only show the name and not the number?

That's because the same number set in your address book is for different contacts. For example, Zhang San's mobile phone number is 123456, but you still have a Zhang Shan number on your mobile phone, which is also 123456. When dialing or answering this number, the mobile phone can't distinguish it. Only numbers are displayed.

The solution is to keep the only one and delete the other.