Hi Thies,
another way coming to my mind is using a different destination instead.
Actually I cannot remember this colleague option (6 seems to be so long ago...). But thinking about it this might be found in the same range as some Superior or Assistant Options I indeed remember.
But what I have in mind and where destination can be defined per user as well would be using Switchboard instead.
If the issue indeed is the prompt itself, I would say the file replacement Thomas mentioned should work perfectly well (Assuming the other prompt is not intended to be used in the system at the same time.)
BR
Alexander