Why are blocked numbers still able to call me?

In the Phone app , do any of the following.

1. Tap Favorites, Recents, or Voicemail. Tap. next to the number or contact you want to block, scroll down, then tap Block this Caller.
2. Tap Contacts, tap the contact you want to block, scroll down, then tap Block this Caller.

Avoid unwanted calls on iPhone - Apple Support

I think the OP is saying they have blocked the number already, but it is still coming through. I blocked a number this morning at 11.30am and the number has since called me twice and it has come through as a normal phone call