Default [Q] Need help with some data issues

So here is the deal, my sister has a Samsung Galaxy S III phone and of late Verizon is saying that she is using tons of data. She has even replaces the phone completely and still it is showing she is using tons of data. The data usage monitor is showing almost no data being used, ie 0.03mb data used and she has data limits setup etc. The new phone itself has nothing installed but default apps.

Is there something that could be causing this outside the phone and what can I have her look for to figure it out. I am sadly not nearby or I would do a full check myself.

I am sure I have not given enough info here, so do ask anything. I will do my best to supply info as needed.

(Edit)Just got the info on the data usage, it shows almost nothing for most of the time then twice it shows downloads of over 500mb.

8/17/2014 7:26 PM 540891.5kb 528.21mb 0.5158343gb
8/17/2014 11:11 AM 657966.8kb 642.55mb 0.627486005gb