That's why they have so many communication issues!
Yes, it is an official rule of 'The Umbrella Academy': no cell phones. You will never see a smartphone in the show, even though the timelines (naturally, except for the 1960s) look quite modern, and the events mainly take place in the 2010s.
Turns out it was a deliberate decision by the showrunners to tick out cell phone technology from the show so that it feels familiar but "slightly different".
So I suppose you could say we're in a little bit of an alternate universe but I want it to feel very, very subtle," showrunner Steven Blackman told Slashfilm back in 2019. "I'm not sure you picked up on it but there are no cell phones. No one uses a cell phone ever. It's odd things like that."
The Sparrow Academy sticks to the plan, with the absence of the common technology sometimes putting characters in weird situations. For example, when Number Five discovered the Operations Bunker of the Commission and saw his 100-year-old self, he had to carve out the tattoo his doppelganger had on his chest instead of simply taking a picture of it.
Every time a phone call takes place in the show, it is via pay phones: this is how, for instance, Allison reached out to her daughter Claire.
In fact, fans have been in pain over how the lack of smartphones fueled the dysfunctionality of the family.
"That's a really cool detail but omg imagine how many communication problems could've been solved if they could just call each other," – @qualitybumbos.
Still, instead of simply giving each other a call, the Hargreeves have to think of alternative ways of establishing the contact. The role of technology is indeed very suppressed in the show, and it is both a great detail and potentially something that triggered many problems that the family has faced.
However, given the new timeline the Hargreeves discovered themselves in after the season 3 finale, there is a possibility that technology will have a more important role this time. The new world looks a lot more high-tech than anything we saw in 'The Umbrella Academy' before, with the city being filled with illuminated skyscrapers.
Who knows whether we are ready for the Hargreeves family to familiarize themselves with smartphones. Chances are it will trigger another round of apocalypses.