There is now an API for applications to block and annotate incoming calls. There isn't a native interface. So, you would need to find an app that does this on the App Store. Or, find an open source project, compile it in Xcode and use your AppleID to install the app onto your personal devices.
One review covering this category is:
The major US carriers are also starting to identify spoofed caller ID. So, you would want to check with your cellular carrier to tighten up which calls and information they send in the first place to the iPhone. Once you’re set there, look at a call screening app that meets your specific needs. The good ones cost money to develop. So, if you are running a free app or don’t understand how they pay their bills, double check if they instead sell your call or location data to fund the app.