The term "call backs" implies a situation where someone has already received a call, and they are now expecting another one. Antonyms for "call backs" could include phrases such as "forward calls", "original contact", or "initial conversation". These phrases suggest a fresh start or a first-time occurrence, rather than a follow-up or repeat interaction. Another antonym could be "one-time communication," indicating that the interaction is not expected to continue beyond the initial exchange. Using these antonyms instead of "call backs" could potentially encourage more personalized and meaningful conversations, rather than simply following up on past interactions.