FaceTime was a utility on an iPhone that allowed the interaction of one person to another through a screen. (TV: Before the Flood, PROSE: Press Play) Its logo was a green rounded square with a white illustration of a camera in its centre, and a white circle in its corner. This white circle, itself, had a green illustration of a telephone in its centre. (WC: The Zygon Isolation)
FaceTime was used by Clara Oswald to speak to the Twelfth Doctor while Clara was on the Drum in 2119 and the Doctor was in the TARDIS in 1980. (TV: Before the Flood)
While recharging the TARDIS, the Thirteenth Doctor used Facetime to contact Graham O'Brien, Ryan Sinclair, and Yasmin Khan. (PROSE: Press Play)
Petronella Osgood had the application installed on her computer by 10 May 2020. (WC: The Zygon Isolation)