"Out of this World" (1964) by Alfred Bester. Here's a stackoverflow post: https://scifi.stackexchange.com/questions/251779/phone-calls-between-man-and-woman-tha

"Out of this World" (1964) by Alfred Bester. Here's a stackoverflow post: https://scifi.stackexchange.com/questions/251779/phone-calls-between-man-and-woman-that-live-in-alternate-universes https://scifi.stackexchange.com/questions/251779/phone-calls...