Once a team member tries to answer a fifth, the alarm will be raised - so try to avoid killing guards when possible.
You won't be able to fool security forever, as a team can only answer 4 pagers per mission day without security getting suspicious. The number of pagers you can answer in a single go is limited. Though it might seem like an inconvenience, this mechanic actually allows for some leeway on the stealth portion of a heist.
A few seconds after you take out a guard, their pager starts beeping - and one of your team members must answer it in the next 7 seconds, or the alarm will be raised.
