Unknown Number (2016)

Home alone, in the dead of night, Lisa is cramming for the exams. It is almost three in the morning, and she is fighting to keep her eyes open, when all of a sudden, Lisa's smartphone rings. Who could that be at this kind of hour, and why does the stranger keep calling? After a while, the frustrated student is tempted to pick the phone up, however, would you answer a call from an unknown number?