Battery drops with suspected background apps
The battery on my iPhone8 often drops unexpectedly. I had turned off all the "background refreshes", notifications, location services. I checked the battery statistics, I saw that the iMessage and Gboard apps were using the battery in the background. Last several weeks, the same things happened, which the apps such us Mail, Calendar and a few other apps used the battery in the background. I removed those apps, and now it is happening to iMessage app and perhaps other apps. I always keep my iPhone with the latest iOS upgrade. What is happening to my iPhone? Is it being hacked? Any solutions?
iPhone 8 Plus, iOS 13