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: 638

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
406-638 A Hardin MT CWAGMTXCDS0  2250 PROJECT TEL. CO., INC. 650      
406-638 0 Hardin MT   6010 NEW CINGULAR WIRELESS PCS, LLC 650   2025-10-10   
406-638 1 Hardin MT   6564 CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MT 650   2014-09-05   
406-638 2 Hardin MT   2250 PROJECT TEL. CO., INC. 650      
406-638 3 Hardin MT   2250 PROJECT TEL. CO., INC. 650      
406-638 4 Hardin MT   2250 PROJECT TEL. CO., INC. 650      
406-638 5 Hardin MT   453F ONVOY, LLC - MT 650   2021-07-05   
406-638 6 Hardin MT   771G TELEPORT COMMUNICATIONS AMERICA MT - LLC 650   2020-08-07   
406-638 7 Hardin MT   2250 PROJECT TEL. CO., INC. 650      
406-638 8 Hardin MT   453F ONVOY, LLC - MT 650   2021-07-05   
406-638 9 Hardin MT   2250 PROJECT TEL. CO., INC. 650      

Last updated: Thu, 29 Jan 2026 14:35:03 UTC

Sponsored by: Execulink Telecom

Like this site? We accept donations via PayPal.