53i, disable ignore softkey?

I am running Aastra 53i phones at my office with firmware 2.6.0.66. Our phone personnel are using the "ignore" soft-key option on the phone's display to bypass certain incoming calls and send them back to the call queue. They were doing this with the Goodbye button, but I was able to disable that in the phone's .cgf file. Is there a similar way to disable the ignore function as well? It is difficult to catch them in the act, so I'd like to just disable it.