Tales from the Darkside (1984)

Season 2: Episode 7

A hate-style radio host, Mandrake, spews out venom at anyone who calls in. He soon discovers, however, after receiving calls across all of time that he is dead but that the "Boss," has kept him on since he discourages souls and make them more prone to the "Boss'" influence. Mandrake is unable to leave his broadcast booth and finds himself transforming into a demon as he has to continue broadcasting forever, and ever.