NumberResearch Membership · Data 09/20/2026

Recent prefix assignments

0 prefixes assigned in the last 30 days · from the daily NANPA CO code file, 09/20/2026

Full prefixes (NXX) Thousands-blocks (1,000-number pools)

The Code holder is who opened each NPA-NXX prefix — not necessarily who holds the numbers. A prefix is 10,000 numbers, but under pooling its ten 1,000-number blocks are handed out individually, often to different carriers; the code holder may hold only one block, or none. The Thousands-blocks column shows how the ten blocks are really split — click which blocks → to see who holds each 1,000-number block and its last-4-digit range. Assignments are initial assignments; the current serving carrier may differ due to portability.

Most active assignees, all time — NPA 331
T-MOBILE USA, INC. 42
ONVOY, LLC 39
CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL 33
NEW CINGULAR WIRELESS PCS, LLC - IL 26
FRACTEL, LLC 18
New assignments by month Sep 2026 Aug 2026 Jul 2026 Jun 2026 May 2026 Apr 2026 Mar 2026 Feb 2026 Jan 2026 Dec 2025 Nov 2025 Oct 2025
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Recent NPA-NXX prefix assignments
AssignedNPA-NXXThousands-blocks taken (last-4 opening)Code holderOCNRate centerState
2008-10-22 331-472 0–9 XXXall 10 · 7 holders which blocks → T-MOBILE USA, INC. 6529 NAPERVILLE IL
2008-08-23 331-462 0–9 XXXall 10 · 5 holders which blocks → MCIMETRO ACCESS TRANSMISSION SERVICES LLC - IL 7196 LOMBARD IL
2008-08-19 331-330 0–9 XXXall 10 · 3 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 NAPERVILLE IL
2008-07-30 331-262 0XXX1XXX2XXX3XXX4XXX5XXX7XXX8XXX9XXX · 3 holders which blocks → T-MOBILE USA, INC. 6529 AURORA IL
2007-12-05 331-456 0–9 XXXwhole prefix which blocks → FIRST COMMUNICATIONS, LLC 460K ROSELLE IL
2007-11-05 331-645 0–9 XXXwhole prefix which blocks → T-MOBILE USA, INC. 6529 ELMHURST IL
2007-10-17 331-465 0–9 XXXall 10 · 5 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 W CHICAGO IL
2007-09-20 331-452 0–9 XXXall 10 · 2 holders which blocks → CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL 6333 AURORA IL
2007-09-18 331-575 0–9 XXXall 10 · 2 holders which blocks → T-MOBILE USA, INC. 6529 AURORA IL
2007-09-18 331-643 0–9 XXXall 10 · 2 holders which blocks → T-MOBILE USA, INC. 6529 AURORA IL
2007-07-12 331-684 0–9 XXXall 10 · 9 holders which blocks → RCN TELECOM SERVICES OF ILLINIOS, INC. - IL 8702 AURORA IL
2007-07-11 331-425 0–9 XXXall 10 · 3 holders which blocks → T-MOBILE USA, INC. 6529 AURORA IL
2007-07-06 331-248 0–9 XXXall 10 · 4 holders which blocks → COMCAST IP PHONE, LLC 318J GENEVA IL
— 331-211 not yet reported which blocks → MULTIPLE OCN LISTING MULT IL
— 331-241 0–9 XXXall 10 · 3 holders which blocks → ONVOY, LLC 224C LOMBARD IL
— 331-258 0–9 XXXall 10 · 4 holders which blocks → ONVOY, LLC 224C AURORA IL
— 331-259 0–9 XXXall 10 · 5 holders which blocks → PEERLESS NETWORK OF ILLINOIS, LLC - IL 063E SUGARGROVE IL
— 331-265 0–9 XXXall 10 · 2 holders which blocks → ONVOY, LLC 224C GENEVA IL
— 331-301 0–9 XXXall 10 · 6 holders which blocks → METROPCS, INC. 5562 AURORA IL
— 331-303 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 4 holders which blocks → BANDWIDTH.COM CLEC, LLC - IL 984E ELBURN IL
— 331-309 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 2 holders which blocks → COMMIO, LLC 939H LEMONT IL
— 331-311 not yet reported which blocks → MULTIPLE OCN LISTING MULT IL
— 331-318 0–9 XXXall 10 · 7 holders which blocks → BANDWIDTH.COM CLEC, LLC - IL 984E LEMONT IL
— 331-411 not yet reported which blocks → MULTIPLE OCN LISTING MULT IL
— 331-511 not yet reported which blocks → MULTIPLE OCN LISTING MULT IL
— 331-555 not yet reported which blocks → MULTIPLE OCN LISTING MULT IL
— 331-591 not yet reported which blocks → IL
— 331-611 not yet reported which blocks → MULTIPLE OCN LISTING MULT IL
— 331-642 0–9 XXXall 10 · 4 holders which blocks → BANDWIDTH.COM CLEC, LLC - IL 984E ELMHURST IL
— 331-700 not yet reported which blocks → IL
— 331-711 not yet reported which blocks → MULTIPLE OCN LISTING MULT IL
— 331-725 0–9 XXXall 10 · 3 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 OSWEGO IL
— 331-811 not yet reported which blocks → MULTIPLE OCN LISTING MULT IL
— 331-825 not yet reported which blocks → DIGITAL NETWORK ACCESS COMMUNICATIONS, INC. - IL 972C GENEVA IL
— 331-911 not yet reported which blocks → MULTIPLE OCN LISTING MULT IL
— 331-950 not yet reported which blocks → IL
— 331-958 not yet reported which blocks → IL
— 331-959 not yet reported which blocks → IL
— 331-976 not yet reported which blocks → IL

Source: NANPA CO Code Assignments (Utilized, All States, Public), file date 09/20/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.