Am the OP - Have a friend who the identical thing happened to. After spending MANY hours with Verizon techs, we have both now ordered replacement MiFis. I cannot think of any program running in the background that would do this. No mapping program, auto updates turned off, no videos, nothing that is a data hog............email and a few websites for a few minutes. You can bet I will be watching like a hawk and monitoring usage. THANKS all for your wise thoughts on this. a few new items were tried and will be used as I move forward. Much appreciation to all.