(https://community.freepbx.org/t/howto-block-offshore-premium-rate-numbers/17447/2)

On the System Recordings page, select Built-in Recordings and build a recording using these settings:

• Name: Blocked
  
• Descriptive Name: „We are sorry, the number you have dialed is currently unavailable. Please contact technical support.“
  
• Files:
  
  • sorry
  • the-number-u-dialed
  • is-curntly-unavail
  • please-contact-tech-supt

On the Announcements page, create a new announcement:

• Name: Blocked
• Recording: Blocked
• Destination After Playback: Terminate call (Congestion)

On the Misc Applications page, create a new application:

• Name: Play blocked message
• Feature Code: *999
• Destination: Announcements (Blocked)

On the Trunks page, create a new Custom Trunk

• Name: BlockedTrunk
• Custom Dial String: Local/*999@from-internal

On the Outbound Routes page, create a new Route:

• Name: Blocked Routes
• Trunk Sequence: BlockedTrunk
• Dial Patterns:
  • prefix: 0900
  • match pattern: .