Yo te hablo
I'll talk to you
Well, it seems like this one is pretty much an open and shut case. And it almost is. Almost.
But don't worry, this phrase really is pan comido.
Yo te hablo is a very informal and colloquial way of telling someone you'll call them back. However, this may be something exclusive to Mexican Spanish. With that in mind, let's take a look at some more universal ways of telling someone you'll call them back.
Te regreso la llamada
Te devuevlo la llamada
One thing you never want to say is:
Llamame pa' tras
This is a bit of English translated literally creeping into Spanish, and in some circles may be used to say "Call me back", but it's absolutely incorrect Spanish and I promise you most native speakers will cringe at the sound of this.
Other than remembering not to use this phrase, the only other thing worth pointing out is that "pa'" is short for "para", and that is something you need to remember, because you'll hear it a lot.
With these simple but handy phrases, you'll be able to return phone calls in Spanish with ease!
¡Hasta la próxima!