NumberResearch Membership · Data 09/20/2026

Thousands-blocks in 443-558

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 443-558 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
MCIMETRO ACCESS TRANSMISSION SERVICES LLC 4
PEERLESS NETWORK OF MARYLAND, LLC 2
OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC 2
VERIZON MARYLAND, INC. 1
PAETEC ITEL, LLC 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
— 443-558-0XXX 0000–0999Reserved MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 ABERDEEN MD
2013-04-04 443-558-1XXX 1000–1999Assigned PEERLESS NETWORK OF MARYLAND, LLC 568G ABERDEEN MD
2013-07-26 443-558-2XXX 2000–2999Assigned MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 ABERDEEN MD
— 443-558-3XXX 3000–3999Reserved MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 ABERDEEN MD
2010-02-17 443-558-4XXX 4000–4999Assigned PAETEC ITEL, LLC 829J ABERDEEN MD
2010-04-12 443-558-5XXX 5000–5999Assigned VERIZON MARYLAND, INC. 9212 ABERDEEN MD
2010-11-04 443-558-6XXX 6000–6999Assigned OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC 6855 ABERDEEN MD
— 443-558-7XXX 7000–7999Reserved MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 ABERDEEN MD
2010-11-04 443-558-8XXX 8000–8999Assigned OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC 6855 ABERDEEN MD
2013-04-04 443-558-9XXX 9000–9999Assigned PEERLESS NETWORK OF MARYLAND, LLC 568G ABERDEEN 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.