Well, it doesnt support bluetooth as far as I can see from http://phone.mobile9.com/samsung/i700/. If you are using an external bluetooth card then it must support Object Push Protocol and Hands Free Profile.
This applies to all bluetooth phones for the Prius (and most other cars as well). If these are not available it wont work period.
So check with your bluetooth card maker what protocols and profiles are supported and change the card to one with the correct profiles/protocols if need be.
I purchased the i700, and waited and waited for my Prius. When I finally got it, I tried to enable the promised (in all liturature and the manual it comes with) bluetooth capability by adding a SD card with bluetooth capability. The only such card available on the market is made by Toshiba, so I bought it. Bad move... After multiple calls to both manufacturers, it turns out that Toshiba has no interest in making drivers for any hardware system other than Toshiba, so Samsung is not even a possibility. Samsung still insists that such a connection is possible - however they cannot identify a vendor that produces it and they have no plans to make one themselves. After returning the Toshiba SD card, I threw out the stupid i700 phone (which after freezing on me multiple times did not make a fan out of me) and bought the Motorola V710 which works GREAT!