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.
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Switch: WSSPMTXCDS0

NPA-NXX BLOCK Rate Centre Region OCN LATA LIR Eff date Disc date
406-547 A White Sulphur Springs MT 3310 TRIANGLE TEL. COOP. ASSN., INC. 650      
406-572 A Martinsdale MT 3310 TRIANGLE TEL. COOP. ASSN., INC. 650      
406-632 A Harlowton MT 3310 TRIANGLE TEL. COOP. ASSN., INC. 650      

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

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