I want to prevent that users can change certain functions on their telephone devices such as changing Ringtones or Network settings. Can someone help me where I can disable/enable such settings on CallManager 5.0?
Give this a try, disable the Settings Access parameter on the Phone configuration page. Complete these steps:
From the Cisco CallManager Administration page, choose Device > Phone, and click on the phone for which you want to prevent access to the Settings Button.
Choose Disabled for the Settings Access parameter under the Product Specific Configuration section.
When Settings Access is enabled, you can change the phone network configuration, ring type, and volume on the phone. When you disable Settings Access, the Settings button is completely disabled and no options appear when you press the button. The option Restricted is also available in Cisco CallManager version 4.1(3) and later. When you change Settings Access to Restricted, you can only access User Preferences and volume settings. By default, Settings Access is enabled.
From this doc;
Hope this helps!