The other night I fully charged and backed up my phone to my MacBook, unplugged it, closed every open app, and put it at my bedside and went to bed. I randomly awoke at about 6:00-7:00am and noticed the battery was down to 78% somehow. So I checked the usage and it said it had been in use for 1hr 30min!? I doubled checked to see if any apps were open and literally not one was (other than settings now). Where could this usage have come from and why? I found that very weird. I'm on a limited data plan too, so hopefully it wasn't anything big.