Why is my data usage so high after switching to At&T?

When I had my iPhone 4 with Verizon, I used roughly 300MB of data per month. I recently upgraded to the iPhone 5 and switched to AT&T. Yesterday, at the end of the FIRST DAY of the billing cycle, I checked my data usage --- 500MB! I was barely on the phone at all yesterday. I probably checked Facebook 3-4 times and refreshed my twitter feed a couple times as well. I get about 50 e-mails per day. Can anyone tell me why this is happening?

There's currently a bug with the iPhone 5, iOS 6 and AT&T that causes you to use data even when you're on Wi-Fi.

  • Why is the data usage on my iPhone so high? I can't figure out what I'm doing that is causing it to be so high. I've compared to family members who seem to use the same if not more than I do. I frequently make sure I have Wi-Fi on hoping this'll reduce it?
  • Why is my email usage so high on my iPhone 4? My iPhone email is using a LOT of my data. For example, I just switched to T-Mobile and after 1 day my usage is 120 MB with 106 of that being mail. I even have it set to not load images automatically and it is still very high. Any ideas? I do have 4 email accounts on it. WIth about 2 hours left in the day I've gotten 55 emails today.
  • Under settings on my iPhone, does the data usage include Wi-Fi usage? Because its stating a ridiculous amount and I've had my data off… And my Wi-Fi on. Does the total of data include the amount of Internet I'm using when on Wi-Fi? I'm so confused
  • IPhone: settings cell usage vs AT&T's data usage number? AT&T has a number, by calling it will send you a text message telling you how much usage you have used on your data. But also in the iPhone there's a cellular usage count in the settings app which also tells how much data you have used. Both of my cellular usage counts are different. Which is right?