Here are the following steps that help you "block websites on iPhone permanently?"
Go to Settings > Screen Time.
To activate Screen Time tap Turn On Screen Time then complete the instructions that follow.
Open Settings then activate Content & Privacy Restrictions under the Screen Time section.
Tap Content Restrictions > Web Content.
Choose Limit Adult Websites. Users can rely on this option to block access to numerous adult websites.
From the Never Allow window select Add Website to input the particular website URLs that need blocking.