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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NPA: 520 [Rate centres in NPA 520] [Dial plan for NPA 520]

NXX: 737

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
520-737 A Sierra Vista AZ TCSNAZMAXPY  710A ALLO COMMUNICATIONS, LLC - NE 668   2024-08-16   
520-737 4 Sierra Vista AZ   321J HD CARRIER LLC 668   2025-10-31   
520-737 5 Sierra Vista AZ TCSNAZMAXPY  710A ALLO COMMUNICATIONS, LLC - NE 668   2024-08-16   
520-737 6 Sierra Vista AZ   321J HD CARRIER LLC 668   2025-10-31   
520-737 7 Sierra Vista AZ   321J HD CARRIER LLC 668   2025-10-31   
520-737 8 Sierra Vista AZ   321J HD CARRIER LLC 668   2025-10-31   
520-737 9 Sierra Vista AZ   321J HD CARRIER LLC 668   2025-10-31   

Last updated: Thu, 16 Oct 2025 03:04:18 UTC

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