JedFonner.com

I've noticed a big discrepancy in the amount of 3G data my iPhone 4 says I've used versus the amount AT&T says I've used.  This is a big deal for me because I opted for the lower-tier, 200MB data plan.  Yesterday I ran a test to see how big the difference would be between my iPhone 4 usage meter versus AT&T - the results shocked me.  Note: I am running the latest iPhone software (iOS 4.2.1) and my phone is not jailbroken or modified in any way.

I normally leave the "Cellular Data" toggle in Settings to OFF on my phone to conserve data.  So when I started my test at 7:30 in the morning, I checked my iPhone and the AT&T website and switched the "Cellular Data" toggle to ON. My iPhone usage meter reported that I'd already used 1006KB of "Cellular Network Data" sent and 4.1 MB received so far in my billing period.  So my starting point according to my phone was a total of 5.1 MB of 3G data used.  According to AT&T, I'd used 6.3 MB out of 200Mb.  So at the start the numbers were already a little different but not by too much.

I proceeded to use my phone as I normally would (checking Twitter, reading RSS via Reeder, browsing the web) and I didn't do any large downloading.

At around 7pm, I turned off the "Cellular Data" toggle on my Phone and checked my usage.  My phone reported 1.5 MB of data sent and 7.1 MB of data used - for a total of 8.6 MB. So subtracting my starting point, my phone was telling me that it had used 3.5 MB of data.  AT&T told a different story, however.  According to AT&T, I had now used 56.2 MB of data. Subtracting my starting point, that means AT&T says I'd used a whopping 49.9 MB in one day of casual 3G use.

Long story short, AT&T is telling me that I used over 10x as much data as my iPhone 4 cellular data usage meter is reporting.

Here's a screenshot of my data usage as reported by AT&T:  

According to AT&T, most of the data is due to three big chunks of usage.  I find it hard to believe that I could download close to 40MB of data in one sitting (around 6:10pm) over 3G. 

Something is seriously messed up here.  I called AT&T and asked for a detailed log of all the IP addresses to which I sent and received data, but the level 1 support rep said that wasn't possible and when I asked to speak to his manager, he said the manager would have to call me back. Unsurprisingly, I'm still waiting for that call back.  But AT&T was adamant about the fact that their usage meter reports the accurate usage and my iPhone 4 usage meter must be wrong.  I called Apple and asked if, as AT&T says, their iPhone 4 usage meter is broken, but they said no.

Before you start arguing that I must have a bum phone, I performed similar experiments last month and got similar results, so I took my phone into Apple and got a new iPhone 4.  I then took my new iPhone 4 into an AT&T store and got a new SIM.  But the problem persists as you can see.

Needless to say, I have more faith in my iPhone usage meter than AT&T.  I think AT&T is overreporting data usage to push me towards purchasing the more expensive 2GB data plan.  I've found, however, that I can leave 3G data turned off and survive most days just on Wi-Fi.  I can't check Twitter as I'm crossing the street, but I probably shouldn't be doing that anyway.  But as soon as Nicole and I can ditch AT&T and switch to another wireless carrier, we'll be making that switch.  AT&T, you just pissed off yet another customer.

For others in my boat, here are some tips that have helped me:

• You can have AT&T send you a free text message with your current data usage by calling *DATA# (*3282#).  I set this as one of my phone favorites. It's faster than using the myWireless app from AT&T.
• AT&T doesn't report usage instantaneously. It sometimes takes 12-24 hours for usage to be reported by AT&T, so keep that in mind.
• If you do think you have a bad SIM, call AT&T and ask for one - they'll ship it to you free or you can walk into a store and get one no questions asked.