a telephone based switching system with voice prompt

For $30 this type of project would be doable only as a hobby... If you don't find somebody like that I can put two or three weeks of work into it (and this is why my bid is so over the shown budget). However, I would still need to know details like on what OS and where do you get the audio from. If there's also noise in the background, do you plan to train your own voice commands, etc... Kind regards, x3x7