Verizon Data plan and "Delayed Data"

Question

Had something very odd happen with the Verizon data usage on my Xoom over the course of the past two days.
I'm a fairly heavy user (3 Gbyte plan), and, as such, I do watch my usage using "My Verizon" - both the on-screen widget icon and via longing in to check.
Anyway, on Monday, the screen icon was showing a bit over 2 Gb had been used (cycle ending on the 12th), and later that day (7th) I got the alert text indicating that I'd reached 75%.
I took note of this, and decided to limit how I would use my Xoom so as to avoid going over.
But, Tuesday, I got the text alert that I'd reached 90%, and a check of the widget icon and logging in showed my usage at 2.77 Gb. I put my Xoom into Airplane Mode until I was at home, and my WiFi connected (I made sure that it was using WiFi). I didn't do a great deal with it that would have required much data transfer, even though in WiFi mode.
However, this morning, when I arrived at work (no WiFi, so in 4G) the icon indicated that I'd used 3.055 Gb - over 300 Mb more than when I'd shut-off my 4G/3G usage by going in to Airplane Mode outside of WiFi range. I was perplexed and concerned. I logged in, and sure enough, I was over-limit. I used it for a short while, then put it back into airplane mode (a bit concerned that something was amiss).
A short time later, I turned the 4G back on, and found the data usage had increased to 3.154 Gb – nearly an additional 100 Mbytes (without my even using my Xoom).
I put it back into Airplane Mode, and called Verizon to try to figure out what was happening.
I was eventually connected to someone in tech support, and after explaining what had been happening (turning 4G back on found my usage had gone up to 3.188 Gb), without my even asking if it were even possible, he quickly told me that it was not possible for data usage to be “stolen” (and I neither had tethering enabled, nor the Bluetooth on).
I continued to explain that I was not using my Xoom any more than normal (less, in fact); and he came to this answer for what might have been going on (drumroll, please…):
Delayed Data Usage
He went on to explain that “they see this happen all the time”, and that there can be these “delays” in tallying-up data usage that can extend back 90 days.
I argued that over 400 Mb seemed a rather excessive amount to have been “backed-up”, and suddenly pushed through.
He agreed, but said that there was nothing that could be done.
I have insufficient understanding to argue the point any further, so it seems I will have to accept that I will be charged for an additional 1 Gb (okay, it’s only $10, but it the ****** principle of it!).
So, what I’d like to ask of you all is, has anyone else ever heard of this “Delayed Data” or had something similar happen to you?
I concerned that this large-scale unexplained data usage will continue, and I’ll end up getting hit for even more overages, and I’d like to be better armed to argue my case should that occur. Any explanations of this would be greatly appreciated.

Answer 1

I actually talked to the Verizon rep about the automatic updating of apps (I beleive that I have it turned off for all my apps).
Now, I do have the Eye-Fi app which loads photos from my camera to my Xoom, but the option to upload those photes to Eye-Fi's web site is set to only happen when connected to WiFi. I did take some photos ove rthe weekend, which loaded to my Xoom. but, even if the Eye-Fi apps had ignored the WiFi-only setting, and uploaded them over 4G, it would have amounted to less than 100 Mbytes of data.
Obviously, so apps simnply do their own thing and send and recieve data without user input, but I've had these apps for months, and this sort of thing has never happened before.
One possible app that I was concerned with that might be able to account for such large amounts of data if it were in some rogue behavior would be Netflix, as movies would obvioulsy be very large data files. But, I have no indication that it (or any other app) has simply downloaded such large amounts of data without my knowledge. If anyone knows of apps which might go rogue in such a way, I'd ertainly like to know about them.
Since I didn't include EVRYTHING in my first post, I'll add a bit more info to consider. I've had my Xoom since Feb 28, so I've already been through a number of billing cycles. My typical data usage has been between 2.5 and 2.8 Gb/mo over all those cysles. And, that amount has often included some heavier usage near the end of the cycle when it seemed clear that I was in no danger of going over.
This months cycle is the first since my Xoom was upgraded to LTE. But, that's the only change. I've been using my Xoom pretty much the same way I have been doing for months. That's why I'm so concerned that there is some more going on than just "delayed data". It's not just that I'm over limit, but that it happened very quickly (from ~2.5 to nearly 3.5 in two days) and is so much more than I'd normally use.
Unless LTE has some unoique quirk to it that it ends up using a whole lot more data than 3G, and more (much more) of that data ends up showing up in this delayed fashion [something that it might be fair to warn user of], then I am concern that ther is something more going on here.