Why is System Services using so much data on my 12 Mini?

Over the last month, System Services has uses 654 MB of the 719 MB of my data, roughly 90%. Calendar and Maps are the apps that were the top data users for the period, but with only 17.8 MB and 17.5 MB respectively.

In System Services, the top data consumers are Messaging Services at 196 MB and DNS Services at 156 MB, followed by Siri at 52.6 MB and Documents & Sync at 47.0 MB.

For comparison, there are two other phones on our family plan, a 13 ProMax and a SE (2020). During the same period, the 13 ProMax used only 1.7 MB for DNS Services and the SE used 44.1 MB. My teenager, with the 13, only used 33.1 MB on Messaging Services!! And my wife with the SE only used 67.9 MB on for Messaging Services. The vast, vast majority of all the texting I do, I do with them, yet Messaging Services usage was 196 MB, 288% more than the closest family member.

What is going on with this?

As FYI...

Wi-Fi Calling is off

Cellular Data is on for only 8 apps and that combined total usage was only 65 MB for the period.

Safari is set to only use data when on Wi-Fi

Find My is turned on, but it is on the other two phones, as well, so that doesn't appear to be a significant item, family-wise

Do Notifications and Background App Refresh use data that doesn't show up as usage on the Cellular Data page for the app? I had these turned on for less than 10% of the apps and those were mostly emergency and utility related. Push Notifications only totaled 33.0 MB of the total for System Services.

Any suggestions appreciated.