Local Calling Guide

Area code/prefix search

Search area code/prefix (NPA/NXX)
  • Effective date searches are available only for US area codes. Our sources for non-US NPA-NXX data do not provide this information.
  • If you want to search an entire area code regardless of activity, leave both the next and past days fields set to zero.

NPA: 406 [Rate centres in NPA 406] [Dial plan for NPA 406]

NXX: 997

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
406-997 A Fromberg MT BLNGMTWEMMD  7421 AT&T - LOCAL 650   2024-03-09   
406-997 0 Fromberg MT BLNGMTWEDMD  624H ONVOY SPECTRUM, LLC 650   2024-03-22   
406-997 9 Fromberg MT BLNGMTWEMMD  7421 AT&T - LOCAL 650   2024-03-09   

Last updated: Sun, 01 Jun 2025 02:18:11 UTC

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