To find out what files are being played during certain parts of the Unity conversation, turn on all of the PhraseServer micro traces in the Unity Diagnostic Tool (UDT), and call into Unity. After you listen to what you want to change, gather the logs, and you'll be able to see the file names of the prompts that were played. This is important because there are several prompts that are copied in several different places. Sometimes people thing they're changing the right prompt only to call back into Unity and here the original prompt.
To change the prompt just record a new one, format it the same as the original, and copy it over the original. Mind you, this is unsupported right now because when you upgrade any custom system prompts you've recorded get wiped out and replaced with the ones that come with the upgrade.
adam
