Last week I received an mail from AT&T that I had used 75% of my cell data usage. In the almost 2 yrs (got the iPhone on 8/31/2013) and have only had 300MB of data and never even came close to using 200MB (generally around 100 MB)of data before. I checked the usage AT&T shows and what used all the data was during the night (12:00 am to 1:00 am)this high mystery usage stared two billing cycles ago but really went nut the current billing cycle. I am in bed sound asleep at that time. I called AT&T and they said some app on my phone was dong that and suggest to clear the data usage statics on my phone before I went to bed and the next morning see what was using data. I did that. In the morning my phone showed no data usage and AT&T showed not data used. I did the same the net night and my phone showed no data used but AT&T showed a few K used just after midnight. Did the same last night and my phone showed no data used but AT&T showed a few K used at 12:00 AM and 3:00 AM. AT&T also said I need to turn cellular data off when at home because even if the I am on my Wi-Fi if cellular data is faster it will use the cellular data instead of my Wi-Fi. AT&T also said maybe my Wi-Fi was going down at night and one of the apps was attempting to access the internet at night this could be the cause. I think this is all BS. The good thing that came out of this is I changed my plan and got 3GB of data and unlimited talk and text and cut my bill $15 per month. I did find a lot of info on line about others having large amounts of data used some even whey they shut their phone off. AT&T even said one person used 9GB of data in two days and he hardly used his phone.
Anybody else experienced this?