I recently got an IPhone 5c and with it came a free table, I'm not sure what kind it is. I gave the tablet to my brother and he keeps the cellular data off and keeps it connected to the wifi. I got messages saying that all the data is almost used up and I don't understand why, I checked to see whose been using it most of it and its the tablet but it shouldn't be because the cellular data is off and it's connected to wifi. How can I fix this?