We have a 7911 phone in the lobby of our office and we only want it to work for internal calls. Has anyone done this or is there any easy to accomplish this?
You will need to add the partiton you created for the lobby phone to the other phones Calling Search Space. Place it near the bottom.
Have a read through this good doc, it should give you a pretty good step by step for what you need. You will need to setup an Internal CSS that only has access to your extensions;
Understanding and Using Partitions and Calling Search Spaces with Cisco CallManager
Hope this helps!