Horror film planning

Opening scene - me and Abbie in the lounge, the phone rings, and we have a 'jokey' conversation, and after I've hung up I say about how it was just a prank caller, Abbie goes home and I keep receiving the phone calls, one says "I just saw your friend leave" etc, in another phone call he says "don't hang up or I'll kill you!" then there is a 3 screen split (me, delivery girl at front door, 'baddy' at back door) I start panicking etc