Hello everyone,
My iPhone 5 already shipped with the 13.1 carrier update. Since day one I had been getting my wifi usage added on my data usage. Every time I downloaded something from iTunes match or watched a YouTube video, this issue would occur. Since the first iPhone in 2007, the wifi turns off when put in sleep mode, which is save power I assume. Now in iOS 6 here is what I have noticed:
I started downloading my iTunes Library onto my new phone (2000+ songs) via iCloud at around 10pm and a sudden 1,5GB data charge was added around 3am. The next thing I did was watch a National Geographic Documentary on the YouTube app at around 12am. The documentary is about 45min-1hr long. Again data was charged (this time 500mb). The next day which happened to be the first of my reset billing cycle I had already gotten the text from verizon claiming that I had exceeded my 2GB monthly usage. However on the Verizon website it said that I had only used about 1,5GB.
After doing A LOT of research, I found out that Verizon did admit to a bug in their notification system that was responsible for notifying the user about exceeding their data limit, when they really had not. I have had this bug occur to me back a few months ago when I was on my iPhone 4 running iOS 5. But that still does not explain why it is being charged as data in the first place. Now 1 month later, the billing cycle has just reset again and I was dedicated to figure out what exactly had been going on. Last night I was on YouTube watching another documentary on wifi. About 20 minutes in, I exited the fullscreen and went to check the data usage, and sure enough it was using LTE and had used about 116mb of cellular data.
So my conclusion is:
Even though the wifi should only turn off when the screen is locked and turned off, in iOS 6, it also deactivates after a certain time of inactivity. That gives explanation to both scenarios:
1. Leaving the phone locked, downloading songs all night.
2. Leaving the phone "inactive", although I am using this term very loosly as you are still utilizing the YouTube app.
So my guess is that the problem lies with iOS 6 itself, not Verizon and not the YouTube app. My advice is to turn off Cellular data whenever you are connected to wifi (at your house, work or public place) and turn it on only when you are on the go.
Please try this yourself. Watch a good ol' National Geographic Documentary and about 20-30min in exit the fullscreen mode and also check your data usage. Was it on LTE? Did it charge you data?
*Note that it may take some time to show up in the Cellular Usage under Settings -> General -> Usage -> Cellular Usage.
Congrats if you made it through all of this text.
Cheers,
Maurice