to telephone someone = to phone someone = to ring someone (up) familièrement : to give someone a ring / a buzz
A local call # a long distance call.
Hold the line, please # Hang up.
An answer machine.

* Establishing identity :
1- This is Mike Baxter = Mike Baxter speaking
2- Who's speaking ? = Who's calling ?
3- Who shall I say is calling ?
4- Can you spell your name, please ?
5- Where are you calling from ?

* Getting the right person / department :
6- Could I speak to Mr So and So, please ?
7- Could you put me through to Mr ..., Mrs..., Miss..., Ms... , please ?
8- Could you put me through to extension 405, please ?
9- I'm connecting you now = I'm putting you through now

* Problems :
10- I can't get through.
11- The line's engaged / busy.
12- I'm afraid Mr X is out at the moment / isn't in today / is on another line
13- Sorry, wrong number.
14- This is a recorded message......... Please speak after the tone.
15- Sorry, we were cut off.
16- I can't hear you. We've got a crossed line.
17- All lines are engaged. Please, try later.
18- Look up the number in the directory.
19- They're ex-directory.
20- Please replace the handset / receiver and try again.

* Solutions to a problem :
21- I'll ring him/her back later.
22- Could you ask him/her to ring me back ?
23- Can I take a message ?
24- Dial number ........

* Ending a conversation :
25- Thank you very much for calling / phoning.
26- I look forward to meeting you / hearing from you soon.