Horror film idea

There is a teenage girl called Summer, she lives with her Mum, Susan and her Dad, Phil. They attend an anniversary party one evening of Susan’s friend’s. Summer gets board and asks to go home early. She arrives to an empty house and goes to bed. Her alarm wakes her up at 7am, as she stirs; she hears her Dad’s voice from downstairs. It sounded different though. Phil is on the home phone reporting a missing person, Summer realises it’s her Mum that is missing. Her Dad told her that she disappeared at the party last night and was nowhere to be seen. Summer goes to school to keep her daily routine as normal as possible, and for her Dad not to worry about her. Phil drives her outside the gates of the school and tells her not to worry. Summer sits at her desk and stares at the clock wanting time to pass by quickly, when, suddenly, her mobile phone rings, reading “Dad calling”. She goes to answer it but before she could say anything, her teacher confiscates it and locks it in her desk droor, telling her that she should know better and to collect it from her at the end of the day. Finally it is 3:30pm and Summer goes to get her phone back. As she heads outside for her Dad to pick her up she checks her phone and it says that she has missed 86 calls from her Dad’s mobile number. She gets into Phil’s car and asks why he rang her, he replies that he’s lost his phone and to answer it because anybody could have it. Later that evening, Summer watches TV in the living room while her dad cooks dinner in the kitchen. Summer’s mobile vibrates, lighting up “Dad calling”. She decides to answer it as she is curios who it could be. She hears her Mum whispering on the other end of the phone asking for help. Summer shouts “Mum?” and Phil comes storming into the room snatching the mobile phone from her fingers, he throws it at the front door causing the battery to fall out of it. Summer asks her Dad what he has done. With no reply, Summer runs out of the house, grabbing her mobile phone and battery from the floor as she escapes. The next morning, Summer is sitting on a tyre swing in a wooded area away from the city, with bare trees and autumn leaves along the floor. She suddenly she notices something reflecting the sun into her eyes, she walks up to it hanging on a twig of a bush and sees that it is her Mum’s locket, Summer picks it up and opens it, displaying a photograph of her and her mother. She gets out her mobile phone and tries to ring her Dad’s phone, but there is no signal, so Summer searches her Bluetooth devices and finds one named “Phil’s phone”. She investigates beyond the bush and sees a mound of dirt, she digs up a long wooden box that is bolted up. She releases the bolt and opens the lid of the box, she finds her Mum inside, lifeless, and she was too late. Summer notices her Dad’s phone in her Mum’s hand, she picks it up and looks at it, the battery dies and the phone switches off. All of a sudden her Dad shoves Summer into the box on top of her Mum’s dead body from behind her, on the way down she drops her Dad’s phone onto the floor. Summer pretends to be unconscious after hitting her head on the edge of the wooden box, Phil goes to pick up his phone and Summer quickly hits him around the head with a large branch from a nearby tree. He is knocked unconscious and Summer drags him into the wooden box with her dead mother, she shuts the box and buries it back up. A week passes and Summer is happy in a foster home with new friends and people to look after her. Summer’s phone rings and lights up “Dad calling”.