I just got my Google voice # and I see on my iphone that the person's ID (or number) shows up when they call. I'm assuming that in order to call them back using my new GV number..... 1. I will have to have an app like GV mobile +, correct? 2. Is this the best app available? 3. Those of you who use this, does the app have to always be running in the background if I wish to return the call using the GV number, or how basically does this work when I don't want to call back using my ATT number? Thanks in advance for any info on this!