Hello [calling party] Oiga / ¡Óigame!
Hello [called party] ¡Dígame!
I'd like to talk to ... Quisiera hablar con ...
Who is calling? ¿De parte de quién?
Who is that? ¿Con quién hablo?
You've called the wrong number. Se ha equivocado.
Sorry, I've called the wrong number. Perdone, me he equivocado.
Hold on, please. Espere, por favor.
He/she is not available right now. Ahora no está.
Call him/her later. Llámele más tarde.
Call him/her in five minutes. Llámele en cinco minutos.