I said something once and it didn't turn out so well.

Walking around Rapture is mostly noisy. It's full of screaming or nonsense talking Splicers. And even if there is some kind of silence it's terrifying and uncomfortable; strange noises in the background; a faraway howl; a muffled cry of a little girl. Every sound is alerting and might lead into injudicious panic, which causes trouble or lethal attack. It's better to remain silent and still and it's one of the reasons why Jack is not talking when the radio begins to crack; thankfully it only does so when there is indeed no sign of anybody around him.
"Hey, how ya doin'?"

Jack frowns slightly. How should he actually be doing right now? It's the same insane encounters as always - nothing more than deadly routine. Honestly, it's not a big deal at a place like this. At least he isn't already dead. It should be totally clear for a man like Atlas, who lives in Rapture for a very long time. Even though he isn't really able to watch every step Jack takes. Or does he? Jack wonders if it might be true. Perhaps Atlas is indeed always watching him; observes every task and every battle, which would explain why he always comes up talking in the exactly right time. How strange, that Jack doesn't raise this fact in question until now and it's even weirder that he accomplish any order from a man he barely knows and never met in person.
"Ya ain't much of a talker, boyo. Don't be shy to Atlas. Go on, lad. Say ma name."
Of course, he isn't that much of a talker. Seriously, who would blame him for doing so at a place like Rapture? Talking would mean that he has to drop his guard or to reveal his current position to any foe who could be already near at hand. The thought of losing his advantages because of some stupid chatter is just suicidal. If Jack wants to get out of this hell safe, he should better keep his mouth shut. And by the way, why should it be that important, if he would say Atlas' name? It's not like he doesn't already know Jack's latest position and even if this man doesn't, saying his name wouldn't be that helpful at all. Jack assumes he is just bored, which seems natural regarding to his current situation. Jack is wondering what this man does all the time, when doesn't give him useful advice and telling background stories of the city under the sea.

"Aw. Don't make me beg, son. Just only whisper it."
Perhaps Atlas just needs someone to actually talk to, which would be a really good reason, why he seems so desperate while trying to animate Jack into a conversation. He can imagine that there isn't someone left, who is either sane enough or doesn't attack you out of sudden. Maybe he should give this man a favor for guiding him safely through this hell hole?
"No! Scream it. Please?"
Jack frowns in incomprehension. Perhaps he misheard the man on the other side of the radio. Otherwise he couldn't understand, what the benefit of this act would be, except attracting attention. Jack feels the approach of a very uncomfortable misgiving. It makes him shiver with trepidation and some kind of weird curiosity.

"Groan it. A wee little moan? Heh, maybe when we meet I can … squeeze it out of you. Perhaps even suck it out?"
He opens his mouth for a respond but decides against; it's embarrassing and uncomfortable enough and he really wants to know what's going on inside Atlas' mind at the moment. That's totally unnatural and alarming. Atlas has a family … Well, actually he had a family, but that's not the point. The fact is simply, that this man can't talk like that with him. It feels really wrong and beside that it's unusual goading, which is even more confusing. He feels edgy and his face is flushed. He doesn't really want to imagine how Atlas wants his word come to fulfillment, but he's smart enough to know the intention and it makes him shudder in agitation and excitement.
"Heh~ … Ya would like that, don'tcha? Now … Would you kindly jerk off an' yell my name?"
Jack gasps at this heavily before he takes in a deep breath. Suddenly he's in need of air and feels slightly dizzy, as if the temperature unexpectedly increases; he perceives the heat which is strangely crawling through his body. Hell, yes. He would like that. He shakes lightly and sucks in another heavy breath before he's able to reach for his belt, even if the whole scenario still seems intangible and quaint. Jack comes to the only appropriate decision not to think about anything of this anymore and just does like Atlas has told him. How could Jack refuse? He unbuttons his pants to free his semi-hard erection; Jack shivers as the cold air touches the sensitive flesh and sighs mildly.
He leans back and closes his eyes before his fingers brush his cock lightly. Even this little sensation is enough to elicit a suppressed moan from his mouth. In a flash, he wraps his hand firmly around his member; briskly and erratically strokes until he pants heavy and his cheeks burn from the heat which builds up inside his lower regions, crawling through his whole body.
"I can't hear ya, boyo~." Atlas' voice sounds different as Jack can estimate; deeper and almost luscious. He squints his eyes as he gains in speed and movement; his hips twitch in ecstasy and longing for release, breathy moaning and whimpering reluctant and faintly into the radio.
"Aw, a lil' bit louder, would you kindly?"

Jack swallows hard; overwhelmed by need, while he lifts his voice to groan loudly Atlas' name, earning a definitely pleased sound as response. He's close; thrusting desperately into into his own fist . Moaning unrestrained as if initial difficulties are no longer a problem and the spell is finally broken, "Atlas" becomes some kind of mantra; repeating with every new and forceful stroke. The intensity to much.
He comes hard with a suppressed cry; spilling his seed on his body and clothes, leaving a mess. Jack takes a deep breath like he hasn't gotten any air into his lungs for a long amount of time. It lasts a while until he is able to calm his heart rate and breathing, realizing there is silence at the other end.
He licks his lips nervously, feeling exhausted and strangely ashamed by his actions.
"Well, well~." The radio cracks and Jack sighs in relief. "Can't wait to meet ya in person, kiddo."