A lovely, moving story. I don't want to give too much away about it, other than that it was very well written.
The sounds carry this a lot, from the restrained music to the old-time-y rings of the phones.
I went through the game without making any mistakes. I started again to see what happens if I connect to the wrong source and was surprised to see the positions for each line were different!
It wasn't always obvious which line was ringing at the start of each section. There's a light indicator, but I usually had a bit of trouble tracking it down.