Speaking on the phone

Here's a sample dialogue to get you started.

Caller : Hello! Can I speak to John, please?
You   : May I know who's calling?
Caller : I am Jim.
You   : Ok. Just a minute. I'll get him. Oh, I'm sorry, he's taking a shower at the moment.
Caller : Could you please tell him that Jim called, and ask him to call me back on my cellphone? He's got my number.
You   : Sure, I'll do that.
Caller : Thank you.

Some more ways of asking who's on the line.

1. Who am I speaking to?
2. Who is calling, please?
3. May I know who's speaking?
4. May I ask who is speaking?
5. May I know who I'm talking to?

Expressing pleasure on hearing from someone.

1. How nice to hear from you!
2. How lovely to hear your voice!
3. I'm very glad to hear from you.
4. I'm delighted to hear from you.
5. It's a pleasure to hear from you.