Why didn't I answer the phone and send a message to a former classmate yesterday, and she didn't return it?

You call your classmate, he doesn't answer the phone, he doesn't send a message, and he doesn't answer. There may be several situations.

First of all, he is busy. So that there is no time to answer the phone at all, and there is no time to send and receive other people's information.

The second is that it has very important things to do. You must concentrate. Don't be interrupted.

The third is that I am in a bad mood. Don't answer the phone at all. Reply the message. I just want to be alone.

So don't try to call him at this time. You can leave him a message if you have anything. When he wants to call you back, he will definitely call you back.