The situation is that the agency cannot reach one of the guys that re-started in the last 24hrs. Fortunately, a payment is due to this guy from them, so they have decided not to send out payment, that should prompt this guy to contact them.
This sounds as if this guy has been paid promptly for the last few “jobs” and this is the very first time you are considering to withhold payment? Doesn´t this come a bit late? Until now Mr Spammer and Associates must have made a killing.