Right now, any robocall hacker in the world can instantly take over your phone’s screen, knocking you out of your mobile gaming experience, disrupting you as you check out at the store, or breaking your concentration as you try and type out an email.
And disrupt they do, at a massive scale. Several billion fake calls are received each month in the US. Reports show this is a global problem, with Brazilians averaging 37 spam calls per month. Actually, I’m getting a robocall as I type this very sentence, my second today.
At the telelphony-infrastructure level, it’s a supremely difficult problem that lacks a short-term fix because the underlying protocol is hopelessly insecure.
But from a user-experience perspective, there’s a simple way to make things more manageable. Apple should let incoming calls show up as a banner notification, not a full screen alert.
It’s absolutely bonkers that millions of smartphone users get their full screen taken over by robocallers on a daily basis. Tapping Decline is not a great option because it actually tells the robocaller that you’re with your phone and are annoyed by the call, information I’d rather not give.
The jailbreak community for iOS saw this need years ago, and an app called CallReply tweaked the phone UI to let incoming calls appear as banner notifications.
When will Apple follow suit?
Another exclaims there’s lack of call filtering options available in iOS, I completely agree – as blocking individual numbers is totally ineffective in blocking robocall spam. “I would love to be able to block all numbers coming from my area code and the first 3 digits of my number.. all my robo calls come from a number that looks just like mine.” 
Another points out, the carriers could taking some steps to limit robocalls, but may be dragging their feet because it’s (arguably) in their commercial interests to let it flourish. While I agree there’s a lot the carriers could be accomplishing in flagging “inauthentic” behavior of network participants, the root cause of SS7’s lack of authentication and encryption will remain. But yes, carriers are definitely on the hook for making things better too. 
Yet another commenter remarks about how Google has dealt with this issue: “Fwiw, Android actually does do this. When the phone is unlocked, calls show up as a banner. In addition, they added that new call screening option, I’ve been using it and so far it has worked fairly well. Also, there is some built-in call filtering and third party apps as well, though I have mostly been able to rely on the built-in filtering. Does iOS really not have any options for filtering? I swear last time I had an iPhone (running iOS9) there was Something… but then again, I was jailbroken. It’s a bit funny that we got full web browsers on phones before proper call filtering. (Disclaimer: I work for Google but not on phones.)”