NumberResearch Membership · Data 09/20/2026

Thousands-blocks in 310-507

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 310-507 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 310 blocks

Most active assignees, all time — NPA 310
T-MOBILE USA, INC. 3
MCIMETRO ACCESS TRANSMISSION SERVICES LLC - CA 3
TELEPORT COMMUNICATIONS AMERICA, LLC - CA 1
MCIMETRO ACCESS TRANSMISSION SERVICES LLC 1
LEVEL 3 COMMUNICATIONS, LLC - CA 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
— 310-507-0XXX 0000–0999Reserved MCIMETRO ACCESS TRANSMISSION SERVICES LLC - CA 7240 SAN PEDRO CA
— 310-507-1XXX 1000–1999Reserved MCIMETRO ACCESS TRANSMISSION SERVICES LLC - CA 7240 SAN PEDRO CA
2004-09-14 310-507-2XXX 2000–2999Assigned MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 SAN PEDRO CA
2003-05-16 310-507-3XXX 3000–3999Assigned T-MOBILE USA, INC. 6529 SAN PEDRO CA
2004-04-14 310-507-4XXX 4000–4999Assigned T-MOBILE USA, INC. 6529 SAN PEDRO CA
2004-04-01 310-507-5XXX 5000–5999Assigned T-MOBILE USA, INC. 6529 SAN PEDRO CA
2004-09-02 310-507-6XXX 6000–6999Assigned TELEPORT COMMUNICATIONS AMERICA, LLC - CA 7139 SAN PEDRO CA
2011-11-30 310-507-7XXX 7000–7999Assigned LEVEL 3 COMMUNICATIONS, LLC - CA 8826 SAN PEDRO CA
— 310-507-8XXX 8000–8999Reserved MCIMETRO ACCESS TRANSMISSION SERVICES LLC - CA 7240 SAN PEDRO CA
2012-10-30 310-507-9XXX 9000–9999Assigned BANDWIDTH.COM CLEC, LLC - CA 981E SAN PEDRO CA

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.