Verify if you were charged incorrectly? You can look at your bill and the data use and see when you were billed for whatever amount. You can look back at your phone or Verizon's data utilization tool to see which apps used what data as well. Are you asking about how to find proof that you didn't use as much data as Verizon says you did?
If you have newer Android devices you can go to Settings, Data Usage and review data usage for period in question and see what mobile data usage was.
I had used about 13GB and it was near the end of the billing cycle, I checked my email and that was all I did then I logged off - later that day the account showed the 86GB. I don't think it can be correct.
You didn't say if this is a phone or jetpack? you logged off what, the email client? If it was a jetpack, did the computer stay connected, did the jetpack stay on? How many computers connected. do you have a backup service? Jetpack would make this more plausible. Do you have text warnings for overages turned on? Did they trigger?
does the phone or jetpack also indicate the data was used? You can't get the destination and source ip addresses for your traffic without a court order, which may be worth proving if you should pay $1300.
I checked my email on my phone, I meant I backed out of the mail app - not that I logged out - sorry.
The text warnings for overages are turned on, but for some reason I didn't receive even the normal ones. I am receiving them normally during this billing cycle, though.
I guess I'll have to setup some better overage protection...
Unintentional 86GB is REALLY hard to do on a phone. Something doesn't seem right. Do you use hotspot? I am with you scratching my head on this one.
I agree with Weth 86gb is a LOT of data, like streaming many many HD movies on Netflix or streaming over 10 hours of Ultra HD on Netflix data. If you have a hot spot using data that becomes more achievable especially right now with Microsoft pushing out Windows 10 (and actually pushing it to your computer before you confirm that you even want it depending on your Windows update settings, pushing many people over their data usage in the past month).