Here is the step-by-step guide using the (Settings method), which is the most reliable way to manage your blocked list.

If you know exactly who you want to unblock, you can bypass the main settings list entirely using the Phone or Contacts applications. 1. Using the Phone App (Recents List)

This method works best if the blocked person attempted to call you recently. Open the native app. Tap the Recents tab at the bottom of the screen.