Cellular (2004)

After dropping her son off at the bus stop, doting mum and high-school science teacher Jessica Martin is kidnapped at gunpoint and thrown in an unknown attic with only a nearly-unusable phone. As her world turns upside-down in an instant, the desperate mother manages to jury-rig the device and connects with the cell phone of young college student Ryan. Now Jessica's life is literally in Ryan's hands--and as the ruthless abductors threaten to kill her, Ryan has to act fast to rescue the woman on the other end of the line. However, with a dying battery, how can Ryan save Jessica when this could be her last phone call?