Basically, as soon as other reliable methods became widely adopted. No, I don't have any phone call related anxiety or whatever, I'll call someone if I really need to, I would just rather not. I'd much rather get a text that says, "Hey, we're meeting up at 7pm to go out and do, XYZ, do you want to come?" than a phone call that starts with that and turns to "So anyway, did I tell you my mom blah, blah, blah... And I don't know what to say, because I kind of want to go, but it would be a lot blah, blah, blah."
Phone calls with friends and family have a way of spiraling off into tangents when I don't necessarily have the time to entertain them, but don't want to be a dick all the time telling people I don't have time at the moment to listen to them. If there's a self-service section to a company's website or app, I can usually do whatever I need faster than it would take me to get through the automated menus and hold music to call and have them do it. Like my pharmacy, if I want to refill a prescription online, I log in, check a box and hit submit. Done. If I call them, I need to go through three menus to get patched through to the pharmacy, tell them what I want, hold for a moment while they help someone in the store, give them my info and wait for them to look it up, etc.
When I plan to meet up with people, I make plenty of time to talk to them and listen to whatever. When I get what I think is going to be a short phone call that devolves into tangents, I don't necessarily have the time to entertain whether the fact that my friend's cousin had his toe amputated due to gangrene means he should get the spot on his nipple tested for leprosy, or if he should just improve his personal hygiene and see if it washes off in the shower.
If something really is going to be a pain to communicate via text, schedule that conversation and we can have a call to discuss it, but I'm not answering phone calls whenever somebody calls out of the blue unless I'm interviewing for jobs or expecting a call about some sort of emergency.