Having the same issue. My Cellular Usage on my iPhone (in Settings) is showing 700 MB received since Friday (note that there is a discrepancy somewhere, because My Verizon reports that I currently have used 438 MB of data). I don't stream much video or any music. Mostly just check Facebook, Twitter, look at a couple of web pages. I DID run a SpeedTest 2-3 times on Saturday which accounts for a nice chunk of data on My Verizon, but the largest chunks from that date on the Verizon report show 4:27 AM. Is the timing on these reports off? I was definitely asleep at the time.
Also, at least once a day the My Verizon report shows a 10-30 MB usage and I can't figure out what this is. This occurrs even before I got my new iPhone 5. I'm definitely not downloading apps every day or streaming video/audio. Any idea what these could be? Is there an app that tells you which apps are using how much data?
I'm confused and really don't want to bust over my 2 GB limit on the first month off of unlimited data.
I remember checking my iPhone 4's Cellular Usage before I switched phones and I think I used 2 GB of data in like 6 months. What the hell is going on?!?!