Yes, you can replace the prompts that say this with blank prompts so they don’t play – be aware that this is not TAC supported or supported by the BU. Future upgrades will over write these changes and you'll have to do this again.
You need to replace the prompt in question with a silent prompt (basically blank but not quite empty) so that Unity's conversation code wont get cranky when it goes to look for a prompt it's expecting and it's not there.
So, step one is to find a blank prompt. There are several. I suggest using:
\Commserver\Localize\Prompts\ENU\AvAddrSearch\AvAddrSearchENU003.WAV.
You want to copy this blank prompt over the prompt you don't want to hear. In your case there are actually two different prompts that say the same thing but get used in different places (i.e. if it’s a subscriber vs. an outside caller). The prompts are:
\Commserver\Localize\Prompts\ENU\AvPHGreet\AvPhGreet016.WAV
\Commserver\Localize\Prompts\ENU\AvPHGreet\AvPhGreet037.WAV
These both say "You may record your message at the tone… " thing... This should do what you want. No reboot or anything like that should be required. I'd make a backup of the original prompt just in case you want to go back or this isn't the guy you really wanted to remove. You can also pull it from the original install CD if you get in a jam.
