NumberResearchThousands-blocks in 203-564
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 203-564 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 203 blocks
Most active assignees, all time — NPA 203
New assignments by month
Sep 2026
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Dec 2025
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2003-12-22 | 203-564-0XXX | 0000–0999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC - DC | 4036 | STAMFORD | CT |
| — | 203-564-1XXX | 1000–1999 | Reserved | AT&T - LOCAL | 7421 | STAMFORD | CT |
| 2023-07-06 | 203-564-2XXX | 2000–2999 | Assigned | TERRA NOVA TELECOM INC. | 145J | STAMFORD | CT |
| 2004-03-22 | 203-564-3XXX | 3000–3999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC - DC | 4036 | STAMFORD | CT |
| 2014-08-07 | 203-564-4XXX | 4000–4999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CT | 6388 | STAMFORD | CT |
| — | 203-564-5XXX | 5000–5999 | Reserved | AT&T - LOCAL | 7421 | STAMFORD | CT |
| 2004-07-12 | 203-564-6XXX | 6000–6999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC - DC | 4036 | STAMFORD | CT |
| 2014-08-07 | 203-564-7XXX | 7000–7999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CT | 6388 | STAMFORD | CT |
| 2009-05-18 | 203-564-8XXX | 8000–8999 | Assigned | AT&T - LOCAL | 7421 | STAMFORD | CT |
| 2010-07-21 | 203-564-9XXX | 9000–9999 | Assigned | BANDWIDTH.COM CLEC, LLC - CT | 199F | STAMFORD | CT |
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.