Lock Volume Keys on 40X9 Phone

[Schnee88]

Good day everyone.

The scenario is the next one; The client is a Hospital manager, he tells me the nurses decrese the volume of the 4019 telephones so that the incomming external calls dont ring too loud or dont ring at all.

I've tried to block the access to the settings menu on the telephone, so that they cannot change the ringing volume, but when the telephone rings with an external call, they can press the Volume Keys (+ , -) on the set and change the Ringing volume.

Any idea how to block/dont allow them to do this.

Thanks in advance.

Ubi Dubium Ibi Libertas.