(covers information from several alternate timelines)
A cellular phone, also known as a cell phone, was a portable communications device used by Humans in the 20th and 21st centuries, as well as by some Humans in the alternate reality created in the year 2233.
In 1996, four officers from the USS Voyager – Kathryn Janeway, Chakotay, Tom Paris, and Tuvok – were walking near the Santa Monica pier, when Janeway's combadge beeped and many people near them thought their cellular phones were ringing. (VOY: "Future's End")
In 2024, Detective Preston of the SFPD talked on a cellular phone to the Governor of California, Robert Chen on the state of the Bell Riots. While talking, Chen advised her to move in with a SWAT team. (DS9: "Past Tense, Part II")
In 2241 in the alternate reality, James Kirk's stepfather's Corvette was equipped with a Nokia mobile telephone. His stepfather used this to contact Kirk when he took the car out for a joyride. (Star Trek)