May I ask who's calling?
Formal
Is David there?
Informal
May I speak to Mr. Smith?
Formal
Who is this?
Informal
Can I talk to James?
Informal
Would you like to leave a message?
Formal
Hello. How may I help you?
Formal
Goodbye
Informal
Do you want me to tell him/her anything?
Informal
Thank you for calling
Formal