Uploading voice prompts is a feature of  Enterprise Edition and higher editions.
 - Click on AutoAnswer --> voice prompts
  - In the box next to File Name, click the Browse button.
  - Locate the voice prompt file on your computer.  Voice prompt files must be saved with the following attributes: 
 - Must be a .wav file
  - Must be less than 2 MB
  - Must be PCM 16-bit Mono
  - Must be 8Khz
  
   - Give your voice prompt a Description (optional)
  - Check the box under Local Server only if your computer is on the same LAN as your trixbox Pro 
  - Click "Apply All Changes"