I believe that F8A allows you to remove a license (don't bother looking for information on it, it's not documented). You need to verify the serial number snd note which order it was installed. Most likely the last one listed. Select it then do a CCC to delete it. If you did not get a new IVR registration number when it was added then it should not be an issue. However if you got a new registration number with the addition of the license then you will need to revert back to the previous IVR registration number. Of course this pertains to North American systems.
Every time you add a license you get a new registration number (F83). So when you remove a license you need to do the same thing. Since the previous software serial numbers are the same as before, you can go back to a previous registration number, or reload all licenses. NEC most likely does not have the IVR server on line any more, so you may be out of luck with this entire process.