What does this message mean ?

My sister is trying to call her boyfriend she keeps getting this message that says " the number you dialed has been changed or disconnected ". She said it wouldn't have been changed because he just changed it a few months ago. She hasn't heard from him for a few days she's really worried he wouldn't do nothing to hurt her hes a nice guy so I thought maybe his electric or internet is out but I've seen his brother and sister in law online. What does this message mean ?