Jenny Parker (Sabrina Carpenter) and Lola Perez (Sofia Carson) are teenagers with opposite personalities but the same passion for photography. The two meet when they are finalists for a prestigious photography internship and accidentally switch phones at their interview. Mrs. Anderson calls Jenny's phone, begging for a last-minute baby-sitter. Lola is about to explain the mistake but decides to take the job when she gets served with a parking ticket from Officer James (Max Lloyd-Jones). Jenny's crush Zac Chase (Kevin Quinn) calls to invite Jenny to a Psychic Rockets concert but Lola quickly dismisses him in order to flirt with Officer James. Zac mistakenly believes that Jenny is not interested in him so he decides to take another girl to the concert instead.
Jenny and Lola arrive at the Coopers' and the Andersons' for their respective babysitting jobs. Mrs. Cooper tells Jenny to not let Emily dye her hair and to make sure Katy stays out of Mrs. Cooper's jewelry box. Meanwhile, Lola pretends to be a friend of Jenny's when she arrives at the Andersons and prepares for a relaxing night watching the roller derby obsessed AJ, aspiring chef Bobby, and grounded Trey. Jenny realizes the phone switch and takes the Cooper girls along with her to the Andersons to confront Lola. Bobby's cooking accidentally starts a fire and as the babysitters put it out, Trey sneaks out to attend the Psychic Rockets concert.
Jenny, Lola, and the kids journey in the Anderson's car to a sketchy pawn shop in the city in order to track Trey down to a pawn shop. However, they find that he has already left with his friends. In the shop, Bobby accidentally lets loose a rare Sapphire Ferret and Lola takes a picture of the commotion for her photography resume. Since the animal is illegal, the pawn shop owners chase the seven out of the store, trying to delete the photo from Lola's camera. The group makes it to the car only to find that it is being towed. The truck owner tells them that they need $100 to pay off the car and have until midnight to pay it off. The group is forced to take a bus to their next destination, Trey's favorite pizza parlor. They find Trey and now all together, try to figure out how to pay off the tow truck fees. Bobby spots the pawn shop owners following them and a chase ensues into a clothing factory. The seven once again escape them and once they are safe, Lola suggests re-selling the ticket at the concert.
The criminals still track them down but hold off on revealing themselves when Lola gets arrested for illegally re-selling the ticket. As they wait the police station, Jenny is horrified to see that Emily secretly dyed her hair green angrily reprimands her. Hurt, Emily calls and leaves a voicemail message to Mrs. Cooper, explaining the trouble they are in. In the interrogation room, Lola meets Officer James. He scolds her for trying to scalp the ticket, pointing out that she could have been hurt and is setting a bad example for her baby-sitting charges. Lola finally realizes her impulsivity has consequences and begs to go free to make things right. Meanwhile, in the lobby, AJ meets her roller derby idol Janie Swift when Swift and her roller derby team are brought in on charges for disorderly conduct. Lola is cleared of all charges and when she goes to meet with the group, the pawn shop owners charge in. The derby team starts fighting amongst themselves and provides enough distraction for the seven to get away. Once safe, Katy remembers that her mother keeps a $100 bill in her coat for emergencies and the group decides to sneak into the local planetarium where the Coopers and Andersons are attending a party to steal it for the truck fees. As Jenny, Katy and Lola sneak into the storage room to look for Mrs. Cooper's coat, the Coopers hear Emily's message and head to the police station to check on their children. The coat turns out to be left at the Cooper's table, where the Andersons are sitting, so Lola disguises herself as a wealthy socialite to steal the money. Meanwhile, Bobby takes charge of the catering after the chef quits. Once Lola retrieves the money, the group heads to the tow place before it closes and get the car back. Lola jokes how Jenny's night is more interesting than going to a concert with Zac and Jenny finally learns why Zac has suddenly become distant. She becomes angry with Lola but Lola suggests driving to the Psychic Rockets concert to explain everything. Lola trades her precious camera in exchange for Jenny's admission so Jenny and Zac can reconcile. The group then races home before the parents.
Once they enter, they find out about a much bigger mess. The washing machine has burst, with soap everywhere. The Andersons' dog, Lady Marmalade, is covered with sauce, which is also all over the floor. Trey washes the car and helps Emily clean their dog, Jenny and Katy clean the laundry room, and Lola, Bobby and AJ clean the kitchen. Once they all are done, Jenny, Katy and Emily leave to get them back home, and the Andersons' arrive home, where Lola immediately covers up and says they were great. Jenny does the same, however as she leaves Zac arrives saying he forgot to give Emily her headphones, and the two start dating, much to the delight of Katy and Emily, who are watching. Lola gets her driver's license back from the young police officer.
Eventually, Lola and Jenny begin to adopt some of the others' traits, and Jenny declines her photography scholarship, giving it to Lola, who begins a relationship with the officer she met earlier. At the end, Lola sends the pictures to Katy, Emily, AJ, Bobby, Trey,Jenny and accidentally Helen who is shocked at seeing them when the picture was sent to Lady Marmalade.