iPhone 15 Pro / Extreme mobile data consumption by system services

For two months now, after the update to 18.5, I have had to suffer from extremely high mobile data consumption (more than 10GB per month) through general system services. No real solution from Apple support. They only recommend waiting for a new update (how long?) and having mobile data turned off most of the time (??). At the end of the month I have to buy additional data from the provider. According to discussions on the Apple forums, this problem affects many iPhone 15 owners, but I did not find any solution in their posts. I temporarily blocked access to data for most applications, I only use them on wifi. I set low data mode, turned off wifi assist, limited location services, iCloud backup only via wifi, uninstalled paid VPN. (... but we probably didn't buy an iPhone for this kind of user experience, did we?). Despite these restrictive changes, my mobile data is still being used through system services. I am angry and disappointed. It has been going on for a long time. It is costing me money. On a certain recommendation, I'm testing from today whether "reset network settings (in the Transfer or Reset iPhone section)" will help in this matter. If it helps, I'll let everyone know here. I hope that the engineers at Apple are also trying something (... but for three months?).