The Cellular in the name of the film refers to a cell phone.  Jessica has been abducted and is hidden away in an attic in an unknown location. One of her abductors smashes a telephone that was in the attic and when left alone Jessica attempts to connect some wires and contact someone in the outside world for help. She eventually makes a connection with a young man who tries to help her, but at no time can he lose connection with her as he can’t then phone her back. The film is action-packed from the beginning.

Read more about it here Film Review – Cellular (2004)