NumberResearchThousands-blocks in 406-550
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 406-550 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 406 blocks
Most active assignees, all time — NPA 406
New assignments by month
Sep 2026
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| — | 406-550-0XXX | 0000–0999 | Reserved | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MT | 6564 | MISSOULA | MT |
| — | 406-550-1XXX | 1000–1999 | Reserved | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MT | 6564 | MISSOULA | MT |
| — | 406-550-2XXX | 2000–2999 | Reserved | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MT | 6564 | MISSOULA | MT |
| — | 406-550-3XXX | 3000–3999 | Reserved | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MT | 6564 | MISSOULA | MT |
| 2023-02-08 | 406-550-4XXX | 4000–4999 | Assigned | NUSO, LLC | 732J | MISSOULA | MT |
| 2022-03-01 | 406-550-5XXX | 5000–5999 | Assigned | LEVEL 3 COMMUNICATIONS, LLC - MT | 9415 | MISSOULA | MT |
| 2022-09-16 | 406-550-6XXX | 6000–6999 | Assigned | T-MOBILE USA, INC. | 6529 | MISSOULA | MT |
| 2022-09-16 | 406-550-7XXX | 7000–7999 | Assigned | T-MOBILE USA, INC. | 6529 | MISSOULA | MT |
| 2023-01-25 | 406-550-8XXX | 8000–8999 | Assigned | TELNYX LLC | 073H | MISSOULA | MT |
| 2023-01-25 | 406-550-9XXX | 9000–9999 | Assigned | TELNYX LLC | 073H | MISSOULA | MT |
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.