NumberResearchThousands-blocks in 203-350
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 203-350 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
Aug 2026
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2008-05-01 | 203-350-0XXX | 0000–0999 | Assigned | LEVEL 3 COMMUNICATIONS, LLC - CT | 4800 | MADISON | CT |
| — | 203-350-1XXX | 1000–1999 | Reserved | TELEPORT COMMUNICATIONS AMERICA, LLC - CT | 7143 | MADISON | CT |
| 2010-01-27 | 203-350-2XXX | 2000–2999 | Assigned | BANDWIDTH.COM CLEC, LLC - CT | 199F | MADISON | CT |
| 2010-06-04 | 203-350-3XXX | 3000–3999 | Assigned | BANDWIDTH.COM CLEC, LLC - CT | 199F | MADISON | CT |
| 2014-03-13 | 203-350-4XXX | 4000–4999 | Assigned | CENTURYLINK COMMUNICATIONS, LLC | 508J | MADISON | CT |
| 2007-08-10 | 203-350-5XXX | 5000–5999 | Assigned | SOUTHERN NEW ENGLAND TELCO DBA FRONTIER COMM OF CT | 9147 | MADISON | CT |
| 2019-07-11 | 203-350-6XXX | 6000–6999 | Assigned | ONVOY, LLC - CT | 639C | MADISON | CT |
| 2020-06-05 | 203-350-7XXX | 7000–7999 | Assigned | ONVOY, LLC - CT | 639C | MADISON | CT |
| 2014-06-02 | 203-350-8XXX | 8000–8999 | Assigned | BANDWIDTH.COM CLEC, LLC - CT | 199F | MADISON | CT |
| 2008-10-30 | 203-350-9XXX | 9000–9999 | Assigned | BANDWIDTH.COM CLEC, LLC - CT | 199F | MADISON | 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.