I'm flying to Tokyo on Tuesday, where I'll be picking up a "Pocket Wifi" hotspot to use for the week that I'm there. It's not unlimited data, and I'm worried that my iPhone will go, "Oh hey, wifi!" and proceed to download some gigs worth of iOS 11 on both mine and my husband's iPhones. I'm planning to upgrade to iOS 11, but not in the middle of an overseas trip where my phone is my lifeline for maps, etc. Does anyone know of a way to shut off background downloading of iOS 11 when it's on a wifi connection?