NumberResearchThousands-blocks in 331-261
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 331-261 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 331 blocks
Most active assignees, all time — NPA 331
New assignments by month
Sep 2026
Aug 2026
Jul 2026
Jun 2026
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Dec 2025
Nov 2025
Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2020-08-30 | 331-261-0XXX | 0000–0999 | Assigned | STRATUS NETWORKS | 495J | LEMONT | IL |
| 2021-05-21 | 331-261-1XXX | 1000–1999 | Assigned | IP HORIZON LLC | 515J | LEMONT | IL |
| — | 331-261-2XXX | 2000–2999 | Available | LEMONT | IL | ||
| 2026-06-15 | 331-261-3XXX | 3000–3999 | Assigned | METROPCS, INC. | 5562 | LEMONT | IL |
| 2021-06-08 | 331-261-4XXX | 4000–4999 | Assigned | ONVOY, LLC | 224C | LEMONT | IL |
| 2021-06-08 | 331-261-5XXX | 5000–5999 | Assigned | ONVOY, LLC | 224C | LEMONT | IL |
| 2021-06-08 | 331-261-6XXX | 6000–6999 | Assigned | ONVOY, LLC | 224C | LEMONT | IL |
| — | 331-261-7XXX | 7000–7999 | Available | LEMONT | IL | ||
| — | 331-261-8XXX | 8000–8999 | Available | LEMONT | IL | ||
| 2019-06-21 | 331-261-9XXX | 9000–9999 | Assigned | T-MOBILE USA, INC. | 6529 | LEMONT | IL |
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.