In the film a group of friends start receiving phone calls from themselves on the phones of recently deceased friends. The calls sound like they're made moments before they die. They then try and work out whose phone made the first call in the hope that they can explain what's going on.
I'm sorry, but we've seen this sort of thing before (in films like Final Destination) and it just wasn't scary. There's been a recent fad of making horror films that started their live in Japan. It wouldn't surprised me if this film killed the trend stone dead.