NumberResearchThousands-blocks in 303-243
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 303-243 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 303 blocks
Most active assignees, all time — NPA 303
New assignments by month
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| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| — | 303-243-0XXX | 0000–0999 | Reserved | N.E. COLORADO CELLULAR, INC. | 6874 | DENVER | CO |
| — | 303-243-1XXX | 1000–1999 | Reserved | N.E. COLORADO CELLULAR, INC. | 6874 | DENVER | CO |
| 2006-12-14 | 303-243-2XXX | 2000–2999 | Assigned | T-MOBILE USA, INC. | 6529 | DENVER | CO |
| 2007-03-13 | 303-243-3XXX | 3000–3999 | Assigned | ELECTRIC LIGHTWAVE LLC DBA ALLSTREAM | 3467 | DENVER | CO |
| 2007-09-20 | 303-243-4XXX | 4000–4999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC | 6010 | DENVER | CO |
| 2007-02-27 | 303-243-5XXX | 5000–5999 | Assigned | PAETEC ITEL, LLC | 829J | DENVER | CO |
| — | 303-243-6XXX | 6000–6999 | Reserved | N.E. COLORADO CELLULAR, INC. | 6874 | DENVER | CO |
| — | 303-243-7XXX | 7000–7999 | Reserved | N.E. COLORADO CELLULAR, INC. | 6874 | DENVER | CO |
| — | 303-243-8XXX | 8000–8999 | Reserved | N.E. COLORADO CELLULAR, INC. | 6874 | DENVER | CO |
| — | 303-243-9XXX | 9000–9999 | Reserved | N.E. COLORADO CELLULAR, INC. | 6874 | DENVER | CO |
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.