Hello ElleJacky,
There are a few things you can check on to see if it will resolve this issue with the blocked callers.
Check Settings > General > About and make sure iOS 16.3 is the version showing installed. If not, you will want to update your iPhone. See Update your iPhone or iPad - Apple Support.
Next, do you have any third-party call blocking apps installed? If so, try disabling the app and see if this continues. See the section "Set up an app to filter and detect spam calls" found in the article you posted from, Detect and block spam phone calls - Apple Support.
If you still are getting the blocked callers, reach out to Apple Support so they can look into this with you further.
Take care!