IPhone

iPhones were a type of mobile phone on 21st century Earth. Patricia Menzies mentioned them to the Sixth Doctor. (AUDIO: The Crimes of Thomas Brewster)

Clara Oswald had an iPhone. (TV: The Time of the Doctor, et al.) During the Twelfth Doctor's imprisonment in the Prison, Clara's iPhone was incinerated. (PROSE: The Blood Cell) Clara obtained another and, in her form, Bonnie used the phone to record video and send and receive video calls, while Clara, connected to Bonnie's mind, sent text messages to the Twelfth Doctor without Bonnie realising. (TV: The Zygon Inversion)

The members of the Coal Hill Year 8 Gifted and Talented Group all had iPhones. In the 21st century, when Earth had become overrun with trees, they used Samson's to take selfies. (TV: In the Forest of the Night)

The Twelfth Doctor also had an iPhone, which he used to call Clara and Bonnie, in her form, multiple times. (TV: The Zygon Invasion, The Zygon Inversion)

The Thirteenth Doctor had another iPhone which she used to attempt to contact UNIT, only to learn that its operations had been suspended. (TV: Resolution) She later used an iPhone to contact through WhatsApp. (TV: Spyfall)

Courtney Woods had an iPhone as well, and she used it to post pictures of the Twelfth Doctor on the Moon onto Tumblr in the year 2049. Clara Oswald noted that to the Doctor. Even though he said she couldn't just put pictures of him online he was later able to use the online pictures via her phone to lead her back to him in the TARDIS. (TV: Kill the Moon)

Sonya Khan used an iPhone. (TV: Demons of the Punjab)

In 2020, a Doctor Who fan called UNIT in the 1970s with her iPhone. (WC: U.N.I.T. On Call)

Other similarly named devices from that era included the iPad and the iPod. (TV: Dark Water, A Day in the Death)

Behind the scenes
In the 2019 Doctor Who television story Rosa, Graham O'Brien claims the identity of "Steve Jobs" while in 1955 Alabama, and claims to be developing a telephone capable of playing music, taking photographs, sending letters, and serving as a calendar. This describes many of the iPhone's varied functions. In the real world, Steve Jobs was a co-founder of Apple, the company which produces iPhones.