"거기 지금 몇 년도죠?”
"What year is it there?"
오랜만에 집으로 돌아온 ‘서연’(박신혜).
Seo-yeon (Park Shin-hye) has returned home after a long time.
집에 있던 낡은 전화기를 연결했다가 ‘영숙’(전종서)이란 이름의 낯선 여자와 전화를 하게 된다.
In the house, there is an old phone that connects her with an unfamiliar girl named Young-sook.
‘서연’은 ‘영숙’이 20년 전, 같은 집에 살았던 사람이란 사실을 깨닫고 그때부터 두 사람은 우정을 쌓아간다.
Seo-yeon realizes that Young-sook lives in the same house as her, only 20 years in the past, and the two girls start to form a friendship.
“내가 말했지, 함부로 전화 끊지 말라고.”
"I told you not to hang up the phone carelessly."
그러던 어느 날, ‘서연’과 ‘영숙’은 각자의 현재에서 서로의 인생을 바꿀 위험한 선택을 하게 된다.
One day, Seo-yeon and Young-sook make a dangerous decision that changes both their lives in the present.
‘영숙’은 20년 전 죽은 ‘서연’의 아빠를 살려주고, ‘서연’은 ‘영숙’의 미래를 알려준 것.
In the past, Young-sook saves Seo-yeon's father who had died, and Seo-yeon tells Young-sook about her future.
그러나 자신의 끔찍한 미래를 알게 된 ‘영숙’이 예상치 못한 폭주를 하면서 ‘서연’을 위협하기 시작하는데…!
However, once Young-sook knows about the terrible future that awaits her, she starts sending an unexpected surge of threats Seo-yeon's way!
금기를 깨버린 전화 한 통 살인마가 눈을 뜬다.
Seo-yeon hangs up the phone, breaking their promise, and a murderer opens her eyes*
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*My thought process behind the final sentence: It makes no sense to me when reading it just as it is - something about a phone call that breaks a taboo and a murderer's eyes opening.
The only thing that makes sense to me is that "taboo" refers back to "I told you not to hang up the phone carelessly" (aka hanging up the phone = taboo) which is how I landed on this translation.
So, having read a synopsis of the film, I think the "금기" in the last sentence is probably referring to how the two characters have changed their past/future with their phone calls. The line you refer to, “내가 말했지, 함부로 전화 끊지 말라고,” reads more like someone's response to disobedience of a demand than a broken promise, and confusingly, while it occurs in the middle of the text here, I suspect that in the chronology of the film the line is spoken after or around the time that things get pretty violent and murderous. Like the other text you translated this is some very stylised text, omitting and rearranging details for added suspense, but I think given the lack of context your translation works quite well.
That could make sense. Thank you so much for the help! Do you know if there's a place where I can find short texts that might be a little more straight forward here at the beginning? As you've pointed out the language has been quite stylized which has made me scratch my head in confusing multiple times, haha. Would blog posts maybe be better? Or do you think they might have too much slang?
Blog posts could be good, although you might have to look around quite a bit to find something suitable for your level since people's writing styles tend to vary a lot. You could also take a look at 교보문고, which is an online bookstore that lets you preview (미리보기) the first twenty or so pages of most of the books in their catalogue. A bit tricky to navigate IMO but you can search for books by genre, target age group, and whether they're domestic or foreign (국내도서 and 외국도서, respectively), among other settings.