Nos identificamos...

My name is ______.
This is _______ (here).

Si preguntamos por alguien...

Could I speak to _____, please?
Could you put me through to _______, please?
Could I have extension 123, please?
I'd like to speak to ________ , please.

Explicamos el motivo de la llamada...

I'm calling to ask about...
I'm phoning to tell you about...

Si queremos dejar un mensaje...

Could you give ____ a message?
Could you ask ___ to call me when he gets back?

Agradecemos la atención...

Thanks you very much for your help.
Thanks for the information.

Cierre de la llamada...

Good bye.
Bye.