IPhone 5 confusing Wi-Fi data with Cellular?

Question

I bought my iPhone 5 just a few hours ago. When it was set-up, naturally it used 4G to access the Internet. Once I got home, I connected to my home Wi-Fi.
It is my understanding that the iPhone will always prefer Wi-Fi to 3G or 4G. Plus, the entire night while I used it, I never saw anything other than the WiFi symbol in the corner.
I got a text message from Verizon saying that I had used 75% of my allowed data. (2GB on the plan, but it is prorated) I checked MyVerizon, and it said I had used 427 MB of Cellular Data!! I clicked a link to open a detailed chart, which informed me of only four instances of Cellular data, which totaled up at 1.8 MB. This is a number that makes sense.
So I turned off Cell Data entirely, but left the Wi-Fi on, and continued to download videos from YouTube. Moments later, I got another text from Verizon saying I had used all my prorated data! I checked and Cellular Data was still off! The note even said "With this turned off, all data will be restricted to Wi-Fi"! So I clearly didn't use Cell data, but Verizon thought that I did! Now I'm over my limit and possibly in huge trouble.
The figures given seem consistent with my overall usage, though 99% of this usage was on Wi-Fi. I would stake my life on that fact. No joke. Is it possible that my Wi-Fi data is somehow being confused with Cell Data, even though it's turned off?
In the morning, I'm going to visit the store that I bought it from. However, any info that you guys can give me would really help.
Thanks.

Answer 1

I am having the same issue. I am going to call Verizon this morning. We purchased two new phones and only used them on LTE for about an hour while we went to dinner. All the other time we were in our house with WiFi indicated on the phone. I checked by usage after finding this post, 318 MB used on the new Verizon shared data plan. Each phone used over 150 MB. The only thing we were doing was surfing the internet and sending iMessages while we were at dinner. I looked back at the items that I was doing in the house and I remember after activating the phones and doing a backup that each phone had about 40 apps that needed updated. I believe that 150 MB per phone was due to this period of time.
This is a great example of Apple and Verizon not informing the consumer of a money making feature on the new phone. Verizon promoted the shared data plan to me in the fact that by using WiFi when available would mitigate any overage on data. Apple doesn't inform the consumer that there is a cellular over WiFi feature as there was on the Beta version. I sure hope this gets fixed because I have only once in the last two years ever used 150 MB of data in a single day. We normally only use 1.5 GB in a billing cycle. UGH!!