[teknologist]

I've noticed that he has an app called "Whoscall" installed providing Caller ID in the Phone app. I wonder if this has access to Messages on the phone and is able to read/upload SMS?

A quick search online suggests that this is a Chinese app.

[ncw96]

It is my understanding that Apple’s API for supplementing Caller ID info (and also optionally blocking calls) requires an app to provide a database of numbers in advance, and the system queries that database locally. The app does not get any access to call history or Messages history.