Apologies if this is not in the correct forum.

I need help with swapping over phones.  1st is digital and 2nd is analog.  Physical location is being swapped but extension numbers staying the same (ie the user with the analog phone is getting the digital but keeping their extn #. 
I want to know if this can be done via programming or if physical changes need to be made.  If they werent keeping extn #'s then I would just repatch at the panel tie.  Lines just need to be changed from analog to digital and vice versa.
Thanks for your help.