The last three months I have had my Bell internet speeds capped because we have exceeded our 600GB data cap. Today, only the 17th of the month, I get a notice that it is about to happen again. I looked on the Bell router to see details of usage, and find that my wife’s iPad, which is on but hasn’t been used is hogging the data:
I see that having switched it off, most of the info there has been scrubbed.
Looking at Data Analysis, there is a good deal of stuff related to Mail. Summarizing messages etc. Surely it hasn’t been quietly summarizing thousands upon thousands of e-mails has it?
If I understand you and the graph you shared correctly, that means your wife’s iPad has transferred approximately 300 GB of data without much actual use. Even if that includes some iPadOS updates plus a lot of email, that’s a lot of data.
My top guess would be to check for streaming media apps (video, podcasts, music) downloading and caching content, even content that hasn’t been ordered. Another possibility would be subscribed Podcasts or purchased Music set to download automatically.
For example, before I stopped using Amazon Prime, I noticed that the app would download shows I had never expressed any interest in watching and then suggest that I try them. Insanity! (I think I eventually found the setting to turn off that “service,” but I stopped using Prime and removed it from my devices in protest of declining service and increasing surveillance.)
None of those things seem to apply here. Some of it might be explained by Photos updating with new images she has put on her Mac.
Maybe there is a clue in that she has had this iPad since August, and the data cap issue has only arisen in the least three monthly billing cycles. I may have installed a software update three months ago that started this behaviour. I see 26.4.1 and 26.4.2 were released in April.