As life revolves and time processes, things are changing, what we knew as correct is being substituted for good.
This is the beauty of time and evolution, thanks to people who have dedicated their lives to researches.
“I’ll call you back” sounds absolutely correct but it’s out dated, it’s just like saying “I’ll bring it back” well there’s nothing wrong with that statement but you don’t want to sound outdated, the best way to say that is “I’ll return it”, don’t call back, call again or return it.
“I’ll return your call”
“I’ll call again” those are smart ways to say it.