One way to customize the "front-end" of a Assistant plug-in:
Create a new Auto Attendant.
Record a greeting in the "Play this greeting before offering menu choices" section under the 'General' tab. Such as "Welcome to Acme Corporation".

On the menu choice screen, for the 'nothing' option, set the attendant to transfer to, as an example, the Call Router. You could also check 'Process all other digits as user extensions' under the 'Menu Choices' tab, so the caller could type and extension and quickly by-pass the Call Router is desired.
Also, if desired, add a menu option for the pound key (#) and give it the action of User login. Then a caller can access their TeleVantage account in the traditional way using the Touch Tone (DTMF) buttons. This is an important option when conditions such as a noisy environment prevent effective voice recognition.

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