NumberResearch Membership · Data 09/20/2026

Thousands-blocks in 443-637

This prefix’s ten 1,000-number blocks and who holds each — 10 on record · from the daily NANPA thousands-block report, 09/20/2026

Full prefixes (NXX) Thousands-blocks (1,000-number pools)

The ten 1,000-number thousand-blocks inside prefix 443-637 and who was initially assigned each. Under pooling these blocks often belong to different carriers — the single prefix-level “assignee” is usually just the pool / code holder, not who holds the numbers. ← all 443 blocks

Most active assignees, all time — NPA 443
PEERLESS NETWORK OF MARYLAND, LLC 3
MCIMETRO ACCESS TRANSMISSION SERVICES LLC 3
LEVEL 3 COMMUNICATIONS, LLC - MD 2
ONVOY, LLC - MD 1
BANDWIDTH.COM CLEC, LLC - MD 1
New assignments by month Sep 2026 Aug 2026 Jul 2026 Jun 2026 May 2026 Apr 2026 Mar 2026 Feb 2026 Jan 2026 Dec 2025 Nov 2025 Oct 2025
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Recent thousands-block assignments
AssignedThousands-blockLast 4 digitsStatusAssigneeOCNRate centerState
— 443-637-0XXX 0000–0999Reserved MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 ARGRGBSNIS MD
2004-12-28 443-637-1XXX 1000–1999Assigned LEVEL 3 COMMUNICATIONS, LLC - MD 6119 ARGRGBSNIS MD
2010-11-03 443-637-2XXX 2000–2999Assigned BANDWIDTH.COM CLEC, LLC - MD 071F ARGRGBSNIS MD
— 443-637-3XXX 3000–3999Reserved MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 ARGRGBSNIS MD
2003-01-27 443-637-4XXX 4000–4999Assigned LEVEL 3 COMMUNICATIONS, LLC - MD 6119 ARGRGBSNIS MD
— 443-637-5XXX 5000–5999Reserved MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 ARGRGBSNIS MD
2012-09-12 443-637-6XXX 6000–6999Assigned ONVOY, LLC - MD 876D ARGRGBSNIS MD
2012-09-17 443-637-7XXX 7000–7999Assigned PEERLESS NETWORK OF MARYLAND, LLC 568G ARGRGBSNIS MD
2012-09-17 443-637-8XXX 8000–8999Assigned PEERLESS NETWORK OF MARYLAND, LLC 568G ARGRGBSNIS MD
2012-09-17 443-637-9XXX 9000–9999Assigned PEERLESS NETWORK OF MARYLAND, LLC 568G ARGRGBSNIS MD

Source: NANPA Thousands Block Assignment Report (All Regions, Public), file date 09/20/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.