System services using mobile data
Hello,
I've been having a problem with an iPhone allegedly using mobile data despite it being turned off and also manually disabled for all applications.
I've recently came upon this tpoic https://discussions.apple.com/thread/8333141 which seems to point out that it's impossible to prevent iPhone from using data for it's system services?
My problem stems from my plan, where I'm not paying for data in bulk but am charged per day of usage, so I'm charger rather high amount for the usage of ~400bytes of data by iPhone system services?
Is it truly impossible do prevent this from happening? In addition, why are system services using mobile data DESPITE being connected to wifi?
iPhone 7, iOS 14