Ok, so i'm due for an update and im gonna get the Droid as my new phone. But first, a question. I know about the $30/month data plan that is required, that's fine. But everywhere i read, i also see something about adding a voice plan of at least $39.99/month. My current plan is already $90/month with 3 other lines added.. Do i still need to add this "voice plan" and if so, why??