welcome to the Polycom Community.
Could you provide more details in what you are trying to archive and also the currently used software version?
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services
I dont know of any way to prevent the volume from being adjusted by the user mid-call, but you can certainly request that the phone not remember the volume setting that the user left it at when the call ended with. You would do this by using the voice.volume.persist.* parameters in your configuration file, where * can be any one of 'handset', 'headset', or 'handsfree', depending on which volume you wish to lock down. Setting any one of those to "0" will cause the phone not to remember the last volume setting that the user left the handset, headset, or handsfree speaker at.