Local Calling Guide

Area code/prefix search

Search area code/prefix (NPA/NXX)
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NPA: 857 [Rate centres in NPA 857] [Dial plan for NPA 857]

NXX: 550

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
857-550 A Belmont MA SOVLMAAB6MD  939H COMMIO, LLC 128      
857-550 0 Belmont MA   939H COMMIO, LLC 128   2023-11-26   
857-550 1 Belmont MA   939H COMMIO, LLC 128   2023-11-26   
857-550 2 Belmont MA   939H COMMIO, LLC 128   2023-11-26   
857-550 3 Belmont MA   939H COMMIO, LLC 128   2023-11-26   
857-550 4 Belmont MA   939H COMMIO, LLC 128   2023-11-26   
857-550 6 Belmont MA   490J DISH WIRELESS, LLC 128   2024-05-16   
857-550 8 Belmont MA   892D ONVOY, LLC - MA 128   2024-03-08   

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

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