If the phones are setup for Outside Dialtone Preference, they will grab the highest line that's available to that extension. If the extension is programmed to be able to access both line groups 9 and 8, it will include grabbing lines in group 8. I suggest looking to see if those extensions have access to group 8, and remove that group. I don't think the Original IVX had the option to remove a line group program from a line, altogether (the later systems allowed you to press Hold to delete the line group, thereby changing it to an "Incoming Only" line. I may be wrong, though, so I suggest trying that first.

Justin