Data Usage

I purchased a Netgear Nighthawk Hotspot and signed up for the prepaid plan.  I have an off grid property and there is a T-Mobile tower about 5 miles away.  I was at home (away from the property) setting up the hotspot and charging it through the USB connection on my home computer.  The only usage was a quick test to verify a client could connect to the hotspot and have internet access.  

My data usage now shows that I have used over 80% of my data with there being a number of 100MB chunks at a time.  This is over less than a one day period without any clients connected to the hotspot but with the USB connected to my home computer’s USB port.  I’ve now moved the hotspot power source to an adapter and the data usage appears to have been reduced significantly.  I’m hoping this fixes the issue but don’t understand why the hotspot was using 100MB chunks while connected to a computer with a hard wire internet connection????  Also, is there a way to view what the connection/site was that used the data?