I use gotvmail
and it has a great system. You could easily disable the ability for the user to leave a question - but you can set up a FAQ line where users can use their keypad to select certain questions. Then they can listen to the prerecorded answer.
Depending on volume it can cost between $9.95 and $49/month. I`m find using the $9.95 option right now. You`d have a toll free number. There`s a setup fee - but it`s waived (with a $25 credit) if you`re referred (you can use the link above to be referred). I enjoy this service, and if you have a microphone on your computer you can manage it all from the computer, otherwise you can use the phone (or a combination of the two).
I`m not sure how expensive Simple Voice Box is, but this is a great alternative.
A spin-off from my company, now undergoing funding. A real-time, live-event polling program. Engage your audience at your next conference, seminar, talk or retreat!