Let me think about how to integrate a telegram into the story. Since the movie is about seven murders, maybe the killer sends a telegram as part of the seventh message or as a final twist. In the original movie, the killer sends messages to the detectives, so perhaps replacing one with a telegram. Or maybe a telegram was the original method of communication, but in the movie, it's changed to another form. Alternatively, a new story or continuation where a telegram is discovered, revealing a hidden clue.