Hello, is this John speaking?

　　喂，是John吗?

　　Can I talk to John?

　　请问John在吗?

　　Hi, John. It's Alice.

　　您好John,我是Alice.

　　This is Alice speaking.

　　我是Alice.

　　May I have your name , please?

　　请问您是谁?

　　Who do you wish to talk to?

　　您要找谁呀?

　　Yes , speaking.

　　是的,我是。

　　That's me.

　　我就是。

　　You're speaking/talking to her.

　　您正在跟她说话。

　　This is her.

　　我就是。(注: 男的用This is him.)