Phone (2002) on Netflix

Plot summary

Ji-won is a journalist whose articles about a pedophilia scandal brought a stream of menacing calls to her cell phone. She takes a new number and moves into an empty house in Bang Bae that her sister Ho-jung owns with her husband Chang-hoon. The anonymous calls continue anyway. Ho-jung's daughter Young-ju answers one of them, screams and loses consciousness, and in the days that follow she shows a disturbing attraction to her father and a jealous rejection of her mother. Ji-won keeps hearing from unknown callers and catches sight of a long-haired figure at a piano, playing Beethoven's Moonlight Sonata. Looking into the number, she learns that it once belonged to Jin-hee, a missing teenage girl, and that the two people who held it after Jin-hee died under strange circumstances.