Introducing yourself
This is Ken.
Ken speaking
Asking who is on the telephone
Excuse me, who is this?
Can I ask who is calling, please?
Asking for Someone
Can I have extension 321? (extensions are internal numbers at a company)
Could I speak to...? (Can I - more informal / May I - more formal)
Is Jack in? (informal idiom meaning: Is Jack in the office?
Connecting Someone
I'll put you through (put through - phrasal verb meaning 'connect')
Can you hold the line?
Can you hold on a moment?
How to reply when someone is not available
I'm afraid ... is not available at the moment
The line is busy... (when the extension requested is being used)
Mr Jackson isn't in... Mr Jackson is out at the moment...
Taking a Message
Could (Can, May) I take a message?
Could (Can, May) I tell him who is calling?
Would you like to leave a message?