Unaccountable usage of data

I have a 20GB(10GB day & 10GB night)router with you guys and strangely last night my all inclusive night owl data was depleted while I was sleeping and my daytime data is also almost out. I went to bed at 10pm last night, with NO background app refreshments, iCloud back ups or automatic software downloads on yet when I wake up my data has vanished. I use an iPhone and in over a year that I’ve had this router, I’ve always left it on while I slept and this has never happened to me until today. My router has a passcode and I’m the only one with access to it. I called your customer care and a consultant sent me a screenshot of how much data I supposedly used at 12am while I was sleeping. It says that I used around 9GB at 12am then between 07:59 and 08:14 I used just over 2GB,how is that even possible when I was in doctors appointment at that time? This is not the first time that you guys haven’t accounted for data that you’ve ****** from me and never reimbursed me or were even able to tell me what happened to or on what I supposedly used it on. This is totally messed up, you guys are *****ing from us and yet we’re the ones who have to pay for these contracts at the end of the month. If you can’t tell me what exactly happened to it, reimburse me otherwise let’s take this matter further and see how far we can get.