Joe at 2011-04-02 09:38:28:
Haha. It's like The Red Violin, only evil, and a phone number.
What I think you do there is have the latest guy who gets the phone number keep getting phone calls of condolence. Then when he finds out about the curse it's too late -- someone close to him is killed in an accident that should have killed him instead. In trying to get justice for this person, he'll call for help from one of the underworld figures who called before.
I dunno. Something like that. The phone number becomes a self-fulfilling causality loop of tragedy and murder.
A lot of people who want to do it as a horror movie, but I don't think you can fight a phone number in the third act... unless it's some deranged murderer just killing everyone with that phone number.