This is my first cellular iPad. I've been with ATT since my IP5 and since November of this year the IP6. With my iPhone it would take me forever to use up my data (had a 5GB plan). So I added my iPad to the plan and now 6GB are almost finished in 2 weeks. Looking at the usage data it is coming from the iPad. So how come despite seeing that my Wifi is connected to my iPad it is still using cellular data at home?