You can't remove the access to them.
https://supportforums.cisco.com/message/1126657#1126657
The most common way to delete them is via a small script:
https://supportforums.cisco.com/message/1179090#1179090
An option that I would suggest and might be just simpler is to use either an analog phone or an ip phone with no LCD.
That would accomplish all of your requirements.
HTH
java
If this helps, please rate
www.cisco.com/go/pdihelpdesk
HTH
java
if this helps, please rate