NumberResearchThousands-blocks in 573-728
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 573-728 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 573 blocks
Most active assignees, all time — NPA 573
New assignments by month
Sep 2026
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2017-04-20 | 573-728-0XXX | 0000–0999 | Assigned | ONVOY, LLC - MO | 093F | ARGYLE | MO |
| — | 573-728-1XXX | 1000–1999 | Reserved | SOUTHWESTERN BELL | 9533 | ARGYLE | MO |
| 2019-10-31 | 573-728-2XXX | 2000–2999 | Assigned | ONVOY, LLC - MO | 093F | ARGYLE | MO |
| 2019-10-31 | 573-728-3XXX | 3000–3999 | Assigned | ONVOY, LLC - MO | 093F | ARGYLE | MO |
| 2020-06-29 | 573-728-4XXX | 4000–4999 | Assigned | TELNYX LLC | 073H | ARGYLE | MO |
| 2014-06-27 | 573-728-5XXX | 5000–5999 | Assigned | LEVEL 3 COMMUNICATIONS, LLC - MO | 4932 | ARGYLE | MO |
| — | 573-728-6XXX | 6000–6999 | Reserved | SOUTHWESTERN BELL | 9533 | ARGYLE | MO |
| — | 573-728-7XXX | 7000–7999 | Available | ARGYLE | MO | ||
| 2024-02-07 | 573-728-8XXX | 8000–8999 | Assigned | ONVOY SPECTRUM, LLC | 624H | ARGYLE | MO |
| — | 573-728-9XXX | 9000–9999 | Reserved | SOUTHWESTERN BELL | 9533 | ARGYLE | MO |
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.