iPhone 4 on iOS 5.1.1 Using 3G Data on WiFi networks

If you plug your phone into a power source, WiFi will remain persistant. If not plugged into a power source, iPhone will disconnect from WiFi, while in sleep mode, to conserve battery.

It does not matter if you plug your phone into a power source. There are still certain things that will use the cellular data over the wifi.

I am having the same issue. It's not so much a big deal on my phone since I have unlimited data, but on the other phones in my plan, it kills the 200MB plan within a week.

On my own phone, even though it's not a big deal with unlimited, I am now using 3 times as much data as I used to before about 3 weeks ago.

This has only been happening since about the middle of July. I can't figure it out either.

There are two issues in play here. First, as stated by wjosten, WiFi is turned off when the phone is asleep, unless it is connected to power.

Also, the timestamp on entries on your bill or online usage on your carrier's web site are meaningless. The time shown is the time that a summary of usage was posted to the billing system. That usage could have occurred any time in the previous 24 hours.

The only ways to tell when the usage actually occurred is to note the usage at various times during the day (Settings/General/Usage) or install a data monitoring app such as Dataman, which will report all data usage, the time it occurred and where you were when it occurred. Note that Dataman runs in background continuously and will result in less battery life.

Yeah, unfortunately they took Dataman Pro out of the App store, which is the app that tells you what exactly is using your data. The regular Dataman app just reports how much of your data is being used on a given day 😟

I leave my phone plugged in all night while I sleep, and I still get approximately 20MB use during the night, every night.

Here is a copy of my usage report for my phone with the 200MB plan. The data "hogging" began 3 days before the billing cycle ended on the 26th.

I'm now 4 days into the new billing cycle and already at 50% use. This is absolutely rediculous and the fact that wifi stays on and is used when the phone is plugged in is bunk. The phone is obviously using cellular data.

When during the day is it using cellular data? If you don't know you have no idea whether WiFi is on or not. Unless you leave your phone plugged in 24 hours a day and you are still using cellular data you have no idea whether WiFi is on or off. As I said, dataman will tell you. But perhaps you don't want to know, because if you did know you might have no reason to complain.

I have plenty reason to complain.

Dataman is installed, but Dataman does not tell me what exactly is using the data. Dataman only tells me that data is being used.

DatamanPro is the app that will tell me what exactly is using the data, but as I previously stated, it is no longer available in the Apple app store because Apple removed it.

Dataman tells you WHEN data is being used. Does it show using 3G data at a time when you are connected to WiFi and the phone is plugged in to Apple's charger?

Wrong again. That is also a feature of Dataman Pro.

The version of Dataman currently available in the App store does nothing other than tell you what data was used during a given billing period (the entire month) and send you push alerts when you reach the thresholds you set in the app. No time stamps, no specific app usage, that's it.

So, it really doesn't help.

**edit**

Found "Data Usage Pro" which looks similar, but I don't see anything in the screenshots verifying that it splits up the data usage by application and timestamp.

Interesting. My version of dataman, which is not dataman pro, has a setting for Precise Tracking, which tracks usage every 10 minutes. Also has an option for geotagging.

If yours doesn't have that you will have to note usage periodically throughout the day, in particular, when it is plugged in and should be on WiFi.

I know that my 4S does not use cellular data when it is plugged in and on WiFi, so if yours does there is something wrong with it.

Not sure what happened to Dataman, but it sure doesn't tell me much. I don't have that "precise tracking" option in my version of the app, which I downloaded yesterday.

I noted on Dataman's website that the "pro" version was removed by apple from the apple app store, so they may have scaled back their "basic" version that is in the store currently.

I am checking with the developer of the other similar app I found (Data Usage Pro) to see if it will do what I need to help in tracking this issue. I'll post if I get a reply.

Data Usage Pro does NOT track data use by app.

Try turning cellular data off overnight when your iPhone is connected to a power source. If your cellular statement says that there was data usage during this time, then you will know that the statement is not reporting the actual time of usage.

Yeah, I've put it in airplane mode the last two nights and there's NOTHING between the time I turned it off and the time I turned it back on, unlike the other nights that had data logged during the night.

I completely deleted iCloud. I only had "find my phone" turned on before, and that had been turned on since I bought the phone at Christmas with never an issue. I'll leave data on overnight tonight and see if the iCloud has anything to do with it.

You might also want to go to Settings > General > About > Diagnostics & Usage and make sure it is set to "Don't Send".