Although I dont use it myself there are some here who do. If you do a search on "google voice 8350i" you will get some hits. They should be able to answer your questions but....
Here is a link for info on google voice Google Voice
I've been using GV for the past 2 years (back from when it was still Grand Central), and its a fantastic service. I haven't tried the Berry app yet, but I plan to this week. This is one more workaround for the texting issue with Boostberries. If you have a GV number then you can have all of your calls/texts through that number.