R2500 ****** data

I woke up this morning to a string of sms'es, starting at just after 2 this morning. The last sms, just after 7 this morning, stated that I have used R2003 out of bundle data rates, that is equal to around 15gigs of data. Over and above that, the ******* also depleted my 5 gig data bundle. The store says that it was Pinterest who 'uploaded all the pictures on my phone' and that it was 'my fault for allowing the pinterest app to upload pictures using my mobile data connection. Pinterest is NOT a cloud storage space for your pictures. PLUS ive been in pinterest for over 2 years, and this is the first time this has happened. Where did my data go while my phone was off and I was busy sleeping???