I have an iPhone 4 running iOS 6.1. I have a 500 MB data limit with Virgin Mobile. On about the 25 of February I got a text from them saying I had used up 450MB of my data. I checked today, which is the day my monthly bill ends (the 7th of every month) before I reset my data, and I had 792MB of cellular data received and about 85MB sent! I was absolutely floored at how much data I had used in about a week, maybe a week and a half. I definitely limited my Internet use during that period in hopes it would go down, and I only used it when I was at home where we have wifi. I'm almost always on wifi at school, and always on wifi at home, so I don't understand how so much data accumulated. Is there something in Settings that I need to turn on or off, or anything I need to do to prevent this from happening again? The apps I use mainly are Facebook, Instagram.
Please help, as this is very frustrating and costly!
Added (1). Also I reset my data at 8:30 this morning, and if I check it now, I have already 97MB of data (9.5 received and 1.4 sent) used! I used the Internet for about a half hour today for listening to music on YouTube. What is going on?