Hello everyone,
I'm sorry you're having some issues with your devices. One thing to keep in mind is that data is not processed and billed in real time, first your phone collects any usage information for a period of time and then it sends it to the network for billing during off hours, usually it happens every few hours, but can take up to 3 days. I would start by checking for recent and running apps on your phone, many can run in the background and if not closed out completely, will continue to access and use data. The best thing to do to clear any temporary files or running apps from your memory is to reset the phone once in a while.
Thanks,
Dmitriy