Vanished data

I have data that has gone missing literally over night on my mobile ***. I have requested that the matter be looked into because no apps on my phone were running overnight yet I got a notification that I had run out of data. Mind you I had over 400mb before I slept. Now vodacom sent me an EDR report (Ref# S3-88T3K-KSOWG) in which I highlighted to them that the problem happened betwwen the 16 June 2015 & 16 June 2015. I even indicated that in their report it shows in lines 298 & 299 that data was used. I asked for them to explain which app used this data because no app was running on my phone.<br> <br> I havent got any response except for that vodacom said it bills my account according to data used. Now thats where my issue lies because no app ran & I was asleep, so what used my data.. This by the way is the second time data mysteriously vanishes in ,my account. In Feb or March 2015 the same thing happened