Ninguém , conforme abordado na resposta semelhante da pergunta já feita por Walt
Agnes is angered by the fact that her phone keeps ringing and when she picks up, she hears no one and suspects it's her husband Jerry. Now, although this part could be explained in other ways, I believe this situation is set up to at least hint that there's a possibility her mental state is worse than we thought because the phone might've never rang: Jerry denies calling her and the phone's lightbulb never even lights up when it rings. So it's possible that the phone calls are imaginary, but even if they're not, they still might stand for Agnes's desire to hear from her missing kid and to also channel her anger at her husband.
