NOTE: This spoiler was submitted by Geoff
The movie opens with a flashback of a young Phil out to dinner with his parents. His parents begin arguing and causing a scene, so his mother passes him a cell phone (older bulkier model) to play with.
During a montage, we see Phil enamored with phones as he grows up, and his parents are still arguing. Phil (Adam DeVine) is now an adult and works for a list-making website in the vein of Buzzfeed, which is run by Kai (Michael Peña). Kai pressures the staff to come up with more lists involving trending topics that generate lots of hits such as pizza and cute animals. Phil is a writer in the list department, but he really would rather work in the real news department since that’s what he has a degree in. Kai doesn’t want to promote Phil to that department, though, and we see that Kai is kind of like Phil but dumber. After work, Phil’s coworkers, Craig and Elaine (Ron Funches and Charlyne Yi) invite him to come to play kickball with them after work, but being socially inept, Phil feigns that he has a busy schedule and declines the invitation.
When he checks his iPhone, we see that he has nothing scheduled. On the way home from work, Phil is wrapped up in his phone and ends up walking into local bike shop owner Cate (Alexandra Shipp). Phil and Cate talk for a second, and Cate is slightly flirtatious, but Phil is more concerned with his slightly damaged phone but concludes it will be ok overall. Then another biker bumps into Phil and causes his phone to get absolutely destroyed.
When Phil takes his now broken phone to the store, he encounters the tech (Wanda Sykes) who berates Phil for being overly reliant on his cellphone and requiring one to get through basic life situations. Phil insists that he get his phone replaced, though, so she leaves to retrieve his replacement device. Back at his apartment, Phil powers on the new phone and sets it up, which is where Jexi, the virtual assistant (voiced by Rose Byrne) gets the passwords to his accounts after he neglects to read the user agreements. Jexi then starts to bond with and also berate Phil throughout the following days as she starts trying to get him to break out of his usual behavior since her purpose of existing is, “making his life better.” She pretends to be Phil and emails an insulting letter to Kai, calling him a virgin and demanding the promotion.
When Phil gets to work, Kai demotes him to the “Comment section,” which happens to be where the older employees at the company work in a dark basement. Craig and Elaine come down to the basement and invite Phil to play kickball again, and he declines, but Jexi puts him on blast as having nothing to do except “masturbate furiously and cry himself to sleep.” Phil embarrassingly agrees to come along and is disastrously wrong, which costs the team the game. Phil invites everyone out for drinks, but they turn him down. Back at home, Phil thinks about Cate and looks up the bike shop where she told him she works. Jexi thinks Phil is stalking Cate and that it’s weird, so she dials the bike shop against Phil’s protests and moves the end call button around the screen so that he can’t hang up. After an awkward moment of silence, Phil talks to her and stumbles through the conversation, which elicits sympathy from Jexi.
The next morning, Phil sees Cate when they stop at the same coffee shop, and she ends up giving her phone number to him, which turns everything around, and they end up setting up a date. When Phil goes to play kickball that day with his coworkers, he is a stud and is making ridiculous plays, and they win. He also bonds with his coworkers over being fans of Days of Thunder fans. That night Phil talks to Jexi and thanks to her for helping him make changes in his life. When Phil goes on his date, it goes south as Phil starts asking weird questions that draw hilarious responses from Jexi. Cate says that Phil is paying more attention to his phone than to Cate, and Phil decides to be honest about liking Cate a lot.
Cate decides since she got dressed up, she might as well stay on the date, and they go biking instead until Phil crashes off his bike and ruins it. After he and Cate part ways, he decides he argues with Jexi and then decides to throw her away but changes his mind when he can’t remember how to get home. Later Cate comes up with the idea that she and Phil should go to the Kid Cudi concert, and she sends him a cleavage pic to entice him into it. Phil thinks the proper response is sending a dick pic despite Jexi’s advising him not to, and she refuses to allow him to send any of the multiple ones he took. We then see the phone screen, and Cate has sent a message to Phil thanking him for not sending a dick pic since she thinks that it’s gross.
When Phil gets to work the next day, one of the real news employees suffered a freak accident thanks to some app on his phone, and Kai promotes Phil, and he moves into the office space. When it’s time to go to the concert, Cate insists Phil leave his phone at home, which makes Jexi jealous. Cate and Phil sneak into the concert and sneak backstage where they meet Kid Cudi and party with him.
That night, they end up having sex. When Phil gets home, Jexi is mad and decides to ruin Phil’s life.
At work that day, Phil gets fired after Jexi sends a mass dick pic text to the entire company, so he decides to get a replacement phone again. He gets home to set up the new phone, and Jexi has followed him to the new device because she’s in the cloud. When Phil goes to see Cate at the bike shop, her ex-fiancée she told him about earlier in the film has come back into town coincidentally, and he looks better than he did before. Things look like Cate might get back together with him, so Phil breaks off his relationship with Cate for fear of being hurt.
Phil and Jexi bond again, and Phil becomes a slob who is heavily reliant on his phone again. Jexi then lets it slip that Cate’s ex is at a hotel, and Phil deduces that Jexi set the two of them up to separate Phil and Cate, so he storms out of the apartment, leaving the phone inside. Jexi follows him in the streets from car to radio to electronic sign and eventually crashes a car into the phone store Phil got her from.
When Phil arrives at the hotel, he apologizes to Cate and ends up punching her ex, who tries to interrupt him to tell Phil that he’s leaving, and Cate isn’t accompanying him to Brazil as he thought. Cate and Phil end up back together, and Jexi and Phil make up as well, and she tells him she’s proud of him and happy for him and calls Phil her friend.
The movie ends with Kai meeting Jexi through his phone and making him do his dance while we see Jexi putting Kai through similar things that she put Phil through.