Inston-Vee Vinder was given a call device by the Thirteenth Doctor before they parted ways. He carried it with him ever since, and used it to call her after finding himself on the cyber-conversion planet. (TV: The Power of the Doctor [+]Loading...["The Power of the Doctor (TV story)"])
This device was in the Remembered TARDIS. (TV: The Mind Robber [+]Loading...["The Mind Robber (TotT TV story)"])