IMessage

An application was installed on Petronella Osgood's computer by 10 May 2020. Its logo was 2 speech bubbles coming from the bottom-left and bottom-right. The left speech bubble was large and blue, while the one on the right was white and read "...". (WC: The Zygon Isolation)

Behind the scenes
While the application was not named in WC: The Zygon Isolation, the application was named "iMessage" in the real world, and was an instant messaging service.