There are a number of phrases and idioms that are only used when telephoning. Let's first take a look at an example dialogue: Here are the most common:

Operator: Hello, Frank and Brothers, How can I help you?
Peter: This is Peter Jackson. Can I have extension 3421?
Operator: Certainly, hold on a minute, I'll put you through...
Frank: Bob Peterson's office, Frank speaking.
Peter: This is Peter Jackson calling, is Bob in?
Frank: I'm afraid he's out at the moment. Can I take a message?
Peter: Yes, Could you ask him to call me at 212 456-8965. I need to talk to him about the Nuovo line, it's urgent.
Frank: Could you repeat the number please?
Peter: Yes, that's 212 456-8965, and this is Peter Jackson.
Frank: Thank you Mr Jackson, I'll make sure Bob gets this asap.
Peter: Thanks, bye.
Frank: Bye.

Leaving a Message

Sometimes, there may not be anyone to answer the telephone and you will need to leave a message. Follow this outline to make sure that the person who should receive your message has all the information he/she needs.

Introduction - - - - Hello, this is Ken. OR Hello, My name is Ken Beare (more formal).
State the time of day and your reason for calling - - - - - It's ten in the morning. I'm phoning (calling, ringing) to find out if ... / to see if ... / to let you know that ... / to tell you that ...
Make a request - - - - Could you call (ring, telephone) me back? / Would you mind ... ? /
Leave your telephone number - - - - My number is .... / You can reach me at .... / Call me at ...
Finish - - - - Thanks a lot, bye. / I'll talk to you later, bye.

Here's an example of message
Telephone: (Ring... Ring... Ring...) Hello, this is Tom. I'm afraid I'm not in at the moment. Please leave a message after the beep..... (beep)
Ken: Hello Tom, this is Ken. It's about noon and I'm calling to see if you would like to go to the Mets game on Friday. Could you call me back? You can reach me at 367-8925 until five this afternoon. I'll talk to you later, bye.
As you can see, leaving a message is pretty simple. You only need to make sure that you have stated all the most important information: Your Name, The Time, The Reason for Calling, Your Telephone Number.

This images are some examples of phrases used to communicate in telephone: