Local Calling Guide

Area code/prefix search

Search area code/prefix (NPA/NXX)
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NPA: 406 [Rate centres in NPA 406] [Dial plan for NPA 406]

NXX: 558

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
406-558 A Helena MT   7229 MCIMETRO ACCESS TRANSMISSION SERVICES LLC 648      
406-558 0 Helena MT   073H TELNYX LLC 648   2024-10-27   
406-558 2 Helena MT   9415 LEVEL 3 COMMUNICATIONS, LLC - MT 648   2014-10-24   
406-558 3 Helena MT   9415 LEVEL 3 COMMUNICATIONS, LLC - MT 648   2021-10-02   
406-558 4 Helena MT   9415 LEVEL 3 COMMUNICATIONS, LLC - MT 648      
406-558 5 Helena MT   453F ONVOY, LLC - MT 648   2024-05-05   
406-558 6 Helena MT   453F ONVOY, LLC - MT 648   2024-05-05   
406-558 7 Helena MT   453F ONVOY, LLC - MT 648   2024-05-05   
406-558 8 Helena MT   7229 MCIMETRO ACCESS TRANSMISSION SERVICES LLC 648   2025-11-23   
406-558 9 Helena MT   6564 CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MT 648   2004-09-27   

Last updated: Tue, 13 Jan 2026 21:50:02 UTC

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