NumberResearchThousands-blocks in 603-923
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
The ten 1,000-number thousand-blocks inside prefix 603-923 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 603 blocks
Most active assignees, all time — NPA 603
New assignments by month
Sep 2026
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2012-05-18 | 603-923-0XXX | 0000–0999 | Assigned | BELL ATLANTIC MOBILE, INC | 6386 | ROCHESTER | NH |
| 2011-01-05 | 603-923-1XXX | 1000–1999 | Assigned | BELL ATLANTIC MOBILE, INC | 6386 | ROCHESTER | NH |
| 2012-08-03 | 603-923-2XXX | 2000–2999 | Assigned | BELL ATLANTIC MOBILE, INC | 6386 | ROCHESTER | NH |
| 2010-04-07 | 603-923-3XXX | 3000–3999 | Assigned | BELL ATLANTIC MOBILE, INC | 6386 | ROCHESTER | NH |
| — | 603-923-4XXX | 4000–4999 | Reserved | LEVEL 3 COMMUNICATIONS, LLC - NH | 4017 | ROCHESTER | NH |
| 2012-08-03 | 603-923-5XXX | 5000–5999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC - DC | 4036 | ROCHESTER | NH |
| — | 603-923-6XXX | 6000–6999 | Available | ROCHESTER | NH | ||
| 2013-03-28 | 603-923-7XXX | 7000–7999 | Assigned | BELL ATLANTIC MOBILE, INC | 6386 | ROCHESTER | NH |
| 2010-03-31 | 603-923-8XXX | 8000–8999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC - DC | 4036 | ROCHESTER | NH |
| 2009-05-27 | 603-923-9XXX | 9000–9999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC - DC | 4036 | ROCHESTER | NH |
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.