Assuming I'm interpreting your question correctly, you are talking about what I call a "phone swap." When someone moves to a new office, how do they take their number with them? We have a digital system on a 5000, so this may help:
· Identify the two extensions
· Close Session DB Manager (required)
· On an admin handset, press the infinity button and 9932
· Option 2,4,2
· Enter first Ext and #
· Enter second Ext and #
Exit.