Why did my iPhone use so much data?

I just got my iPhone exactly one week ago. I got a 2g data plan because it's the cheapest and I wasn't worried about running over because all my friends have 2g and are always on their phones and say they've never gone close to the limit. However, I just got a text that I used half my data for the month in only one week! I'm paying for the data plan, so I can't afford to buy more or pay if I go over. I'm just confused because it doesn't seem like I should have used that much. I read that certain apps can take up data, so dovish have to delete them or can I turn off the Internet or them or something? I'm not very tech savvy, so I don't really get any of the data plan usage stuff. Here's a list of apps I have:
Facebook
Twitter
Tumblr
Pinterest
Instagram
Hipstamatic
Keek
Netflix
Lose It!
Logo Game
Doodle Jump
Temple Run
Scribblenauts
Draw Free
Fruit Ninja Free
Google Calendar

The problem might be that the internet apps such as Facebook twitter tumblr netflix might be still running even though your not using them to stop these running apps double tap the home button and touch and hold the app until the app starts shaking then press the red button on the top left corner of the app and that will stop the app from running. To turn of your Internet go to settings then general then networks and then turn cellular data off

  • Why does my iphone use So MUCH data? I run an iphone 5 on verizon and my data plan is either 4 or 5 gigs per month but i'm consistently over by A LOT, in december it says i used 13 gigs, and i have no idea how thats possible, i may have watched 2 or 3 netflix episodes, and i check facebook and instagram regularly, but other than that i don't use much data, how is my usage so dang high?
  • Why does my iphone use so much data? - 1 I got the phone two days ago and get 500mb of data a month. Like have already used 400 and was wondering how and why it is doing it. I use a lot of social media and facetimed once the day I got it for 10 minutes. I went into O2 and they told me it was because of an update but it is still using a lot of data. I was wondering if there's a way to stop this
  • Why does my iphone use data over night when cellular data is turned off? Every night I turn off cellular data and leave the iPhone on and one day I wake up and check my data manager and see i have already used 25 MB please help!
  • Why does my iPhone 5 use so much data? I got and iphone 5 3 days ago, the only time I use the Internet I'm on Wi-Fi, but this morning I got a text saying I've already used 95% of my data! Where is it going? I googled it and it seems like a lot of people are having this problem but they are with Verizon on AT&T, I'm with telus