Having same problem. Verizon rep and Apple rep say this is new to them. After doing some searching I found this discussion board. Maybe it is time that the Department of Consumer Affairs, the FTC and a good Lawyer for a Class action suit are contacted to stop this absurdity once and for all.
I have had this same problem twice now.
I am on a 500MB/month shared plan used with two phones. Combined, we normally use between 200MB and 300MB/month.
About 8 months ago, my wife's iphone 4 started doing this. Every day at the same time, it would use a large amount of cellular data. It started around 50MB, then jumped about 50MB each day for a few days.
She doesn't like change so she was still using IOS6, so I couldn't see cellular usage by app in the settings.
I tried talking with Verizon, hoping to get any kind of information about the usage that could help me find the app or whatever was causing it, but they just told me they didn't have that information, but that they could change my plan to a higher data package (gee, thanks a lot).
So, I upgraded IOS, and after the upgrade, the usage spikes stopped. I don't know if it was some patched bug an app was exploiting, or if simply going through the restore process fixed something. Anyway, it was fine, but I was never able to check to see which apps could be using it. We never had the problem again on that phone until she stopped using it.
She switched to use my old iphone 5 over a month ago, and last night, at 3:40am, she somehow consumed 236.90MB of data.
I looked at the cellular usage in settings and that 236MB does not show up anywhere, so this data is not being reported to the OS.
I've gone through turning cellular data off for everything that I can find that she doesn't use. Push notifications are turned off for email. I can't find anything that should be allowing it to consume the data.
I do not keep her phone updated, she is behind by one update on IOS8. I will be updating it this morning and hopefully that will take care of it.
I have so far never had the problem on any of the phones while I was using them (she gets the hand-me-downs). She uses her phone far less than I do. The major difference that I can think of is that I keep the OS fairly up-to-date on mine.
I am very frustrated that the tools I have available to manage my usage are incomplete... IOS reports cellular data usage, yet somehow usage is getting by without being reported... Verizon shows which phone and at what time the data is used, but I can't tell where it is going or coming from or even if it is send or receive data.
About three to six days earlier I read a post here, under "iPhone 5c", entitled "iPhone 5c Data Usage - Possible Fix". In this post it stated that "Apple released a fix for the iPhone to fix using Data vs Wi-Fi. Check for phone Update and make sure that it is Up-to-Date". The author of this post said that after the update, his or her daughter iPhone started using data usage like any other phone. In which case, you need to check if your wife's phone is using "Version 13.1" . It seem like my wife's phone had a maybe reduction in data usage after this update. But I am not holding my breath just yet. ....
It turn out I was given some bad information 3 or 4 months ago. Please disregard that posting. The author of the information was wrong that there was a possible fix from Apple.
Since then I have learned that by design iPhones will drop or disconnect from any WiFi source when it goes dormant. In which case, the iPhone will then most art using your mobile data at that point on, if you have not disable your mobile data. However, I learn from multi-sources that if you keep your iPhone connected to a power source, then it will not go dormant. In which case, your iPhone will stay connected to the available WiFi source.
And this does really work. After we started doing so, we got my wife's iPhone 5c 8GB excessive data usage under control. This is why I purchase her a 9 foot power cord/cable for her iPhone, for use at home.
My daughters phone is still doing this too. have you got any answers yet? She wants to get rid of the phone but she has another year. I just switched to the HTC and love it. Apple sucks!
My iPhone 5c never disconnects from Wifi while dormant even when not on the charger. I've confirmed this with my moms iPhone 5S whose on her own account. If you want to see what is using cellular data on your iPhone then go to Settings > Cellular and scroll down through the list. You can also disable all apps from using cellular data as well unless you specifically enable it.
On a side note, I also have an LG G2 and it never disconnects from wifi while dormant and off the charger. If you want to view your data usage on Android then you open settings and select mobile data and it will show you what apps are using cellular data and the amount its consuming. It also lists the data used while your actively using the app and while its just running in the background.
Well I was just telling what works for me. I have done all that cellular data adjusting and disabling apps, without making any real dent in the excessive data usage of my wife's iPhone 5c 8GB. Plus my wife did not like my making her smart phone into a dumb phone, by disabling various apps and settings. Therefore, I had to come up with a better solution than doing all of that. However, the keeping her iPhone connected to a power source has solve the excessive data usage by her phone.
I am glad you does not or did not have the same issue as we did. So be thankful for that. As for myself, I have not used any of our data usage allowance since 26 October, 2014, with my Droid MAXX. So I am happy with this fact, leaving me only having to worry about my wife's iPhone data usage.
It's a real thing....here's a summary of what I "learned" back in 2014
Here's a little more information I dug up from 2014, when I cared about this more during our time using a limited data plan. Turned out that my hopes that Tumblr was the issue were not completely true, as the 6 hour events kept on happening....there's definitely more going on here.
Would love to hear a technical description from VZW on the 6-hour "disconnect" mentioned below. Wonder if that has some side-effect or interaction with applications that causes the behavior so many people are seeing. This is way above my pay grade, but given people have been complaining about it for more than 5 years and have data (no pun intended) to prove it....it's a real thing.
I think we have this mystery solved, or at least a better handle on it. I don't think any of you need to change what you do or be more conservative in your usage. This is just FYI in case something similar happens to you or you are curious.
The high usage was coming from X's account, but it wasn't because of anything X was actively doing. The weird thing was the majority of X's usage was occurring at exactly six hour intervals, and started sometime before the beginning of the current billing cycle.
Some searching online led me to believe the problem was Apple apps (e.g. iTunes, iCloud) but X doesn't use either of those on x's phone. Further searching led me to this the Verizon Cloud app was the issue (kind of an equivalent to Google Drive & related services) - that turned out to be false as well.
After ~30 minutes with Verizon customer service I was transferred to a 2nd tier technical service rep, Y, who looked more closely at the account. Apart from what I knew already by looking at our account, Y didn't reveal much new about the source, but Y did say that the Verizon network "disconnects inactive 'sessions' after 6 hours". When I asked for more detail, Y couldn't articulate exactly what that meant, but I figured any potentially "heavy" data apps like browsers, social media apps might be the problem.
Independently I (re-)discovered in Settings => Data usage you can scroll down and see how much data each running application uses. This was really the key. X found an application (Tumblr) that had consumed >1GB, so X deleted it. X's account activity has now been back to typical for the last couple of days, so I think that app was the major/only culprit.
The next step is to have X re-install it and choose the "Restrict Background Data" option. That's done by going to Settings => Data, scrolling down to the app of interest, touching it, and selecting "Restrict Background Data". What this should do is prevent that specific application - if it is running - from using data unless the connection is over WiFi.