I "upgraded" my devices (cell phone and data modem and "2 year contract" original purchases in 2009) in 10/2014. In my July, 2015 billing I noticed a MASSIVE increase in data usage AND charges. I began trouble-shooting on ALL MY devices and plans, comparisons of ALL MY previous charges, explanations, and ALL MY usage behaviors going back to April 2015.
Samsung Galaxy S5: GREAT SMARTPHONE (my first) - PLAN: Unlimited Talk/Text paid monthly for Line
Verizon jetpack 4G-LTE: PLAN: 30gigs paid monthly for Line
Verizon Android NoteBook 4G-LTE: $50.00/with Sales Promotion (Never had a NoteBook - New "toy") Paid Monthly for Line, but didn't activate until I had hired a "techy" to teach me what it did - 07/2015.
All my trouble-shooting showed ONLY the discrepancies with the Data Usage, overage charges, suspension "notices", for first day of new billing of 06/28/2015.
On trouble-shooting usages back to April 2015, the HIGHEST data usage I had was 17GIGS.
Thus beginning the fiasco with Customer Service: Blaming me, blaming my equipment and/or software, blaming Social networks, hacked, misuse of equipment (theirs and mine) etc. ANYTHING OR ANYBODY BUT VERIZON.
Tech tiers trouble-shooting by Customer Service AND Financial Services to Level 3 who were the ONLY entity to authorize Replacement of DEFECTIVE device.
I suspended services on the Jet Pack and NoteBook the second week of August AFTER I supposedly had already used 30GIGs of DATA in LESS than a week and was being charged the $15.00 per GIG overage charge. Jetpack
Verizon suspended services on Samsung Galaxy for PAST DUE BALANCE. Past due balance had NOTHING to do with GALAXY OR NOTEBOOK. I continue to pay for the two on account. I AM NOT REASON/S FOR ERRONEOUS CHARGES ON JETPACK UNTIL Verizon replaces defective Modem @ NO CHARGE AND PAYS ME BACK FOR CHARGES ALREADY PAID AND NOT APPLIED TO CORRECT LINE.
The data use you describe is all very possible. You don't say what tools and measuring you did to confirm it wasn't real use. Belief you couldn't use the data is not proof of not using the data.
Your account includes all the devices on each line. The entire account is suspended for insufficient payment. Your contract states that even in a dispute, you must pay all charges.
Any device you owned in 2009 was a 3G speed device. Th new Mifi is 4G LTE speed and would easily use 2-3 times more data. Video is now in high definition, that uses much more data also.
IF you look back at the first smartphones, and how little data they used, it was because they weren't capable of using large amounts of data. Had cell companies predicted how much data could be used just a few years later, they never would have offered unlimited data plans.
IN the past 2 years, screens have gotten larger, that also uses more data.