NumberResearchThousands-blocks in 603-373
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 603-373 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
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| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2000-11-08 | 603-373-0XXX | 0000–0999 | Assigned | COMCAST IP PHONE, LLC | 318J | PORTSMOUTH | NH |
| 2004-10-13 | 603-373-1XXX | 1000–1999 | Assigned | PAETEC ITEL, LLC | 829J | PORTSMOUTH | NH |
| 2001-06-12 | 603-373-2XXX | 2000–2999 | Assigned | AT&T - LOCAL | 7421 | PORTSMOUTH | NH |
| 2021-04-28 | 603-373-3XXX | 3000–3999 | Assigned | TERRA NOVA TELECOM INC. | 145J | PORTSMOUTH | NH |
| 2004-04-01 | 603-373-4XXX | 4000–4999 | Assigned | TELEPORT COMMUNICATIONS AMERICA, LLC - NH | 8299 | PORTSMOUTH | NH |
| — | 603-373-5XXX | 5000–5999 | Reserved | CONVERSENT COMMUNICATIONS OF NEW HAMPSHIRE, LLC | 4053 | PORTSMOUTH | NH |
| — | 603-373-6XXX | 6000–6999 | Reserved | PAETEC ITEL, LLC | 829J | PORTSMOUTH | NH |
| 2005-07-11 | 603-373-7XXX | 7000–7999 | Assigned | PAETEC ITEL, LLC | 829J | PORTSMOUTH | NH |
| 2003-01-23 | 603-373-8XXX | 8000–8999 | Assigned | COMCAST IP PHONE, LLC | 318J | PORTSMOUTH | NH |
| 2000-05-16 | 603-373-9XXX | 9000–9999 | Assigned | PAETEC ITEL, LLC | 829J | PORTSMOUTH | 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.