One Missed Call

Rework of original:

The victims got a call a week before each of their respective murders. They were told they'd be fine if they never missed a call. With jobs and busy lives this was an impossible task. The first call each missed they got a voice-mail. It explained in gruesome detail what their final moments would entail. Now everyone waits in horror to be the next to get that call, and authorities scramble to find the killer before they miss one call.

Different idea, same name:

Protagonist misses the one call they swore they never would; the one from that friend saying they had hoped they would pick up, but this is goodbye. The one who they were closest to, but who had no other friends. The friend you tell yourself you'll check up on, to make sure their okay, because you know they're depressed. They now blame their self for the friend's passing and spiral. The movie follows them through their grief over one missed call.