System Services - General using excessive amounts of mobile data iOS 18

Hi,

I'm having an issue with System Services > General using excessive amounts of mobile data.

I am connected to WiFi most of every day so I'm generally pretty thrifty with my data usage, so common perpetrators are all turned off.

Automatic App Updates - OFF

Background App Refresh - OFF

iCloud Drive Cellular Data - OFF

Wifi Assist - OFF

Low Data Mode - ON

There is an Apple Watch Ultra 2 connected. However, automatic updates etc are turned off!

It does not happen all the time but quite unpredictable it was several GB (!) within a day.

Does anyone know what is meant with 'General' in System Services?

Thank you for any helpful answer,

Seb

PS The general information about cellular data on the support sites weren't helpful.