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.

Switch: HLNAMTMA4MD

NPA-NXX BLOCK Rate Centre Region OCN LATA LIR Eff date Disc date
406-375 3 Hamilton MT 7421 AT&T LOCAL 648   2004-02-08   
406-634 A Helena MT 7421 AT&T LOCAL 648      
406-634 9 Helena MT 7421 AT&T LOCAL 648      

Last updated: Tue, 04 May 2021 15:04:27 UTC

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