If you want to control what music employees have access to, you can limit the music available in the app. To do this, go to Company settings and under Playback devices turn on the toggle for Limit music selection for playback devices. This will apply to all zones on your account. It will hide Home and the possibility to add new music to the iOS, Android, and Sonos players. Please note that this setting only applies to playback devices.
If you want to prevent users from being able to search for music in the app, you need to make sure you connect your device using a pairing code.
With the old Enterprise Windows player, you can't change the playlist from within the app. The admin needs to log into the account here to change the music.