How is my iPhone using so much data?

Try closing off multi-tasked apps as some of poor designed may be constantly using data to fetch information. The default Apple official apps (Phone, Mail etc) should be safe.

Do you use any streaming audio apps? If so, you need to know that unless your phone is connected to a power source, it will switch to 3G data when it goes into standby/sleep mode.

Receiving emails is very minimum. If a specific email is bigger than a certain size (a few hundred KB), it doesnt get downloaded unless you click the button.

It's most likely streaming apps which is using up 3G during standby.

That does seem odd. I'm in NYC in the USA and I generally use between 15mb and 80mb a month of cellular data from AT&T. I'm paying for the 2gb/month plan, but I guess I'm wasting $10/month because I have never, ever gone over 200mb in a month - in fact, I've never gone over 110mb.

I have usable wifi most of the time; at home, at the office, at the homes of most friends and family, and even at many shopping centers and restaurants. Most of my cellular data use occurs when I use Mapquest or some other GPS/mapping app while in the car.

I have a feeling KiltedTim is on the right track with cellular data kicking in while the phone is screen locked, even if you''ve got a wifi connection at the moment the screen locks.

Well, you said you have Facebook. If you have notifications enabled for Facebook and a lot of "friends" it can use a huge amount of data.

soph239 wrote:

No, not really.

Thats silly about switching back to 3g in standby!

Not silly at all. If it didn't your battery would be dead in a few hours. WiFi requires a continuous "handshake" with the router which eats up power, unlike 3G which only uses power when transferring data.

How many email accounts do you have setup? Are they set to Push, Fetch, or Manual?

Also, some Location Based apps you don't fully close out of tend to contineue to use data, since they're sending and receiving loc data, even when locked. One of my favorite games did that for 2 updates till fixed.

if you have an iphone 3gs or 4 here is one great thing you can do. ffirst you double click the home button to your multi-task menu. then you touch and hold one of the icons until a minus appears and the are all moving. what you want to do is hit the minus button on all your apps. this does not delete apps but what it does is when you are not using the apps it stops them from continuing to transfer data through your service provider. i had the same problem as you, did this and it helped my plan get back on track real easy.

iOS: About cellular data usage

http://support.apple.com/kb/HT4146