> - Get an app to block them
I'd soon change my number before resorting to most apps. Unless it's like uBlockOrigin where I just feed blacklists into it, I'm not really okay with giving an organization besides my service provider my call history. Read Nomorobo's TOS sometime, it's a doozy.
This is how the call blocking API on iOS works. The blocker app can only provide a static, pre-set list of numbers to block to the OS, and that's it. It has no access to call history, awareness of calls being received/made, etc. The OS handles all the blocking, referring to the blacklist the app provided earlier, and provides no feedback to the app itself about this.
Of course, this means that call blocking apps have less features than on Android. For example, apps can't dynamically look up a number when a call is revived and make an on-the-fly decision. This is in keeping with iOS' philosophy of "privacy/security over features", vs. Android's "everything is completely open to developers, for better or worse".
It's a bit like what happened in Zimbabwe that devastated that country 20 years ago when all the white farmers were kicked out, but in slower motion.