NumberResearchThousands-blocks in 857-550
This prefix’s ten 1,000-number blocks and who holds each — 8 on record · from the daily NANPA thousands-block report, 09/20/2026
The ten 1,000-number thousand-blocks inside prefix 857-550 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 857 blocks
Most active assignees, all time — NPA 857
New assignments by month
Sep 2026
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2023-09-26 | 857-550-0XXX | 0000–0999 | Assigned | COMMIO, LLC | 939H | BELMONT | MA |
| 2023-09-26 | 857-550-1XXX | 1000–1999 | Assigned | COMMIO, LLC | 939H | BELMONT | MA |
| 2023-09-26 | 857-550-2XXX | 2000–2999 | Assigned | COMMIO, LLC | 939H | BELMONT | MA |
| 2023-09-26 | 857-550-3XXX | 3000–3999 | Assigned | COMMIO, LLC | 939H | BELMONT | MA |
| 2023-09-26 | 857-550-4XXX | 4000–4999 | Assigned | COMMIO, LLC | 939H | BELMONT | MA |
| — | 857-550-5XXX | 5000–5999 | Available | BELMONT | MA | ||
| 2024-04-16 | 857-550-6XXX | 6000–6999 | Assigned | BOOST SUBSCRIBERCO L.L.C. | 490J | BELMONT | MA |
| 2024-02-07 | 857-550-8XXX | 8000–8999 | Assigned | ONVOY, LLC - MA | 892D | BELMONT | MA |
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.