What devices do you have connected to your jetpack?
I really wish the forum mods would make it more obvious when it comes to creating post titles vs the content... now we have no idea what we missed out on.
First of all Jetpacks don't consume data, your personal devices do. If your data plan is starting to reflect high data usage then one or more of your personal devices are to blame. That means that for the time being you should get into the habit of powering on and off your Jetpack only as it is needed. This will curb off the strange or late night download sessions so that they only occur when you are actively using your Jetpack.
From there its a game of cat and mouse to figure out which device is demanding all the data from the VZW network. You have to use isolation techniques in addition to trial and error to find the source of the data leak and put a stop to it. Sometimes that means bringing the device to a hotspot and letting it finish its updates. Sometimes that means a new VZW device. Sometimes that means termination. Adding more data doesn't help the problem, its a band aid at best.
I am having the same issue with both of my daughter's iPhone 5C. I just went through one and went into each app and turned off "use cellular data" to see if that helps. I'm guessing this will cause them to only be able to do what they are doing while within wifi?
Yes, that will restrict them to wifi. You still have system services that can use data. Your process will help you narrow down which app is using the data. In fact, you should see a MB or GB number next to the app where you turn off the app for cellular access under Settings/Cellular. This will tell you which apps are using the most data. Then you can turn one app on at at time for a period of time until you see usage spike. It is usually going to be:
1) Apps that use video, including web browsers
2) Social media apps
Rarely something could be "stuck" such as an app update or an email that keeps trying to download. There are lots of reports of data usage on this forum. Most are the users actually using the data, but just not understanding how. A very small minority is problem a system or device problem. As soon as I heard "Child's phone" in someway, it is the user consuming the data until proven otherwise. That is my experience, including from my very home. Even when they swear they are not using data.
I get that and that was my first assumption. I have already eliminated that to a degree I know a portion of it is from their "important" uses of the phone but what I do know is that the way they use the phone hasn't changed. The only thing that changed was me changing my plan from 2G per phone to 6G shared over 3 phones. Verizon did something here...just need to figure it out.