Thank you all for your replies, some really good suggestions there. I have factory reset this phone a couple of months ago (when on ios18) but it was restored from a backup so may have brought the problem back with it.
It does seem extraordinary that resetting the network setting doesn’t clear something like this (if that is indeed the issue anyway) and also the random nature of the issue, it’ll typically happen when the phone is not even being used and to use Gb’s of data at a time makes me wonder what is being sent/received. I can’t verify but anecdotally it seems to stop if location services are turned off. I believe ‘system services’, ‘general’ are related to location services somehow but not sure and 6+Gb’s of location reports sounds crazy!
I had to report many bugs of this nature since having the phone and it was simply restored directly from my old iPhone 6s. When I first got it and opened the voice memos app for the first time it used about 1.5gb of data without telling me. All iCloud and backups were off and low data mode on for cellular so can’t explain that but it seems similar things keep happening with the cellular data thing.
It looks as though I’ll have to start a fresh again and not restore - can anyone offer advice as to how I can keep apps that I’ve paid for that have since been removed from the App Store? And how I might transfer the many Gb’s of photo and video back to the phone without having to pay extra for iCloud+ (the last time I tried it as a backup method it failed to upload anymore that 50 odd photos in 12 hours) and I was given a refund for it. iTunes isn’t capable of these things anymore like it was in the past is it?
Thanks again everyone for your help, I’ll update if I find a solution (by getting a different phone possibly!)
