key part of that link:
That is not blocking it's just redirecting the call like double-tapping a volume button (to silence) and double-tapping the sleep/wake/power button.
I want to BLOCK as in the annoying caller does NOT get through, does NOT goto voicemail and spamming and filling up my voicemail which then takes more of my time to listen and delete (I don't have visual voice mail and even then same deal).
Also note:
Try blocking another iOS user that has iMessage / iCloud enabled.
receive an iMessage. Tap their contact at the top of the iMessage, more, edit, then block.
upon any initiated phone call or iMessage from them immediately goes through and it reverts your 'blocked' to 'unblocked' This has been an issue since iOS 11.
I have an ex that continuously does this every few months or so, and yes I'm a sucker to start talking/flirting for that little warmth but I've changed my number (not before deleting her contact and ensuring not in my WhatsApp list as well but I'm not changing my iCloud primary address. Therein still leads potential she can do it again even though my number is not in her contact list but I can receive via the email address. Something I'm considering disabling as long as it doesn't affect family members/friends reaching me via iMessage.