The past month or so I have had a similar issues I never had before with my 3G setup, driving up stretches of the NY Thruway as well as around White Plains, NY -- I see full 3G signal bars, but I lose internet radio completely (I just get the spinning circle), I lose voice command (it shows as "unavailable"), one of my favorite features of the car (though too limited), and my google maps go to empty grids.
I don't see how I can show full bars of 3G and have this be ATT's fault, and feel it must be my Tesla, but then again, unlike probably most of you, I an running in V6.2, not 7.1 on my Tesla! And never had this problem before. Hopefully, when V8 comes out, we'll know for sure ( but then again, tesla is incentivized not to fix this problem, if they can fix it from their end -- they'd rather I spend the money upgrading my radio...). We'll see in a month or two. In the meantime, reboot....