Does anyone know how to set the multi-purpose buttons on the phone to ring a specific extension? They are currently set but are no longer accurate (people have changed offices, phones have moved around, etc)

I have the 12 button phone (no display) - every manual I find online makes reference to the multipurpose keys but does not lay out how to set or change them.

Thanks in advance, this has been a thorn in my side and since I'm the IT person everyone is hounding me about it.

You'll need to contact an Iwatsu dealer to make those changes for you. Keymapping isn't an area designed for end-user programming.