Dead Tone (2007) on Netflix

Plot summary

At the University of Dreyskill, final exams are over and The Crew, as the friends are known around campus, is invited to a classmate's secluded mansion in the Colorado hills. Brandon, the host, hopes the weekend will win back his ex-girlfriend Karina, who brings her own friends along. The house was once used as a reality show set, and cameras feed monitors in a watching room. Marcus suggests a round of Seventy Five, a phone game in which a stranger must be kept on the line for 75 seconds and believe what he is told. Detectives Anne Hastings and John Criton, meanwhile, tie a new killing to the children who survived the Waley murders ten years before.