This would be the setting that you should tell your system administrators to look at.

The standard setting is as you can see to allow the volume to be turned all the way down. If this is changed to any other value the min ring volume can not be set to lower than this. Please note that this is a per device/phone setting, so it has to be altered on any/all the devices where this wants to be changed. This can be done via a bulk update, so it's not as terrible as it might first sound.