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
2018-08-27 331-239 0–9 XXXall 10 · 4 holders which blocks → ONVOY, LLC 224C YORKVILLE IL
2017-12-19 331-238 0–9 XXXall 10 · 4 holders which blocks → TELEPORT COMMUNICATIONS AMERICA, LLC - IL 7136 DOWNERSGRV IL
2017-11-07 331-237 0–9 XXXall 10 · 4 holders which blocks → MCIMETRO ACCESS TRANSMISSION SERVICES LLC - IL 7196 NAPERVILLE IL
2017-10-17 331-235 0–9 XXXall 10 · 5 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 ST CHARLES IL
2017-09-29 331-666 0–9 XXXall 10 · 5 holders which blocks → ONVOY, LLC 224C AURORA IL
2017-09-29 331-800 0–9 XXXall 10 · 4 holders which blocks → ONVOY, LLC 224C W CHICAGO IL
2017-09-21 331-244 0–9 XXXall 10 · 2 holders which blocks → ONVOY, LLC 224C NAPERVILLE IL
2017-08-22 331-255 0–9 XXXall 10 · 3 holders which blocks → ONVOY, LLC 224C AURORA IL
2017-08-08 331-232 2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 4 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 W CHICAGO IL
2017-08-07 331-231 0–9 XXXall 10 · 5 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 NAPERVILLE IL
2017-04-05 331-230 0–9 XXXall 10 · 3 holders which blocks → T-MOBILE USA, INC. 6529 AURORA IL
2017-04-05 331-236 0–9 XXXall 10 · 5 holders which blocks → T-MOBILE USA, INC. 6529 WHEATON IL
2017-03-20 331-226 0–9 XXXall 10 · 4 holders which blocks → T-MOBILE USA, INC. 6529 NAPERVILLE IL
2017-03-16 331-219 0–9 XXXall 10 · 6 holders which blocks → TELNYX LLC 073H AURORA IL
2017-03-13 331-233 0–9 XXXall 10 · 7 holders which blocks → TELNYX LLC 073H DOWNERSGRV IL
2016-09-28 331-385 0–9 XXXall 10 · 4 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 AURORA IL
2016-08-23 331-707 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 5 holders which blocks → T-MOBILE USA, INC. 6529 AURORA IL
2016-08-08 331-315 0–9 XXXall 10 · 4 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 LOMBARD IL
2016-07-13 331-757 0–9 XXXall 10 · 7 holders which blocks → T-MOBILE USA, INC. 6529 LEMONT IL
2016-06-02 331-252 0XXX1XXX4XXX6XXX7XXX8XXX9XXX · 7 holders which blocks → TELEPORT COMMUNICATIONS AMERICA, LLC - IL 7136 WARRENVL IL
2016-05-17 331-227 0–9 XXXall 10 · 5 holders which blocks → CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL 6333 SUGARGROVE IL
2016-03-17 331-300 0–9 XXXall 10 · 7 holders which blocks → T-MOBILE USA, INC. 6529 AURORA IL
2016-03-11 331-263 0–9 XXXall 10 · 3 holders which blocks → ONVOY, LLC 224C ITASCA IL
2016-02-17 331-871 0–9 XXXall 10 · 5 holders which blocks → ONVOY, LLC 224C W CHICAGO IL
2016-02-10 331-771 0–9 XXXall 10 · 5 holders which blocks → ONVOY, LLC 224C ST CHARLES IL
2016-01-18 331-716 0–9 XXXall 10 · 4 holders which blocks → ONVOY, LLC 224C WHEATON IL
2016-01-18 331-717 0–9 XXXall 10 · 4 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 OSWEGO IL
2016-01-04 331-775 0–9 XXXall 10 · 6 holders which blocks → COMCAST IP PHONE, LLC 318J DOWNERSGRV IL
2015-12-14 331-401 0–9 XXXall 10 · 6 holders which blocks → LEVEL 3 COMMUNICATIONS, LLC - IL 6115 NAPERVILLE IL
2015-12-10 331-204 0–9 XXXall 10 · 7 holders which blocks → ONVOY, LLC 224C NAPERVILLE IL
2015-09-16 331-998 0–9 XXXall 10 · 5 holders which blocks → CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL 6333 DOWNERSGRV IL
2015-07-20 331-321 0–9 XXXall 10 · 4 holders which blocks → T-MOBILE USA, INC. 6529 AURORA IL
2015-06-25 331-814 0–9 XXXall 10 · 6 holders which blocks → T-MOBILE USA, INC. 6529 NAPERVILLE IL
2015-06-11 331-806 0–9 XXXall 10 · 5 holders which blocks → COMCAST IP PHONE, LLC 318J WHEATON IL
2015-06-05 331-808 0–9 XXXall 10 · 5 holders which blocks → BANDWIDTH.COM CLEC, LLC - IL 984E PLANO IL
2015-04-23 331-901 0–9 XXXall 10 · 4 holders which blocks → BANDWIDTH.COM CLEC, LLC - IL 984E ST CHARLES IL
2015-04-21 331-704 0XXX1XXX2XXX3XXX4XXX7XXX8XXX9XXX · 5 holders which blocks → BANDWIDTH.COM CLEC, LLC - IL 984E KANEVILLE IL
2015-03-03 331-979 0–9 XXXall 10 · 4 holders which blocks → COMCAST IP PHONE, LLC 318J ELMHURST IL
2015-02-20 331-304 0–9 XXXall 10 · 3 holders which blocks → T-MOBILE USA, INC. 6529 BARTLETT IL
2014-12-29 331-310 0–9 XXXall 10 · 5 holders which blocks → BANDWIDTH.COM CLEC, LLC - IL 984E BIG ROCK IL
2014-12-23 331-308 0–9 XXXall 10 · 3 holders which blocks → BANDWIDTH.COM CLEC, LLC - IL 984E BARTLETT IL
2014-12-11 331-701 0–9 XXXall 10 · 6 holders which blocks → CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL 6333 NAPERVILLE IL
2014-11-10 331-276 0–9 XXXall 10 · 4 holders which blocks → CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL 6333 ST CHARLES IL
2014-10-27 331-253 0–9 XXXall 10 · 4 holders which blocks → T-MOBILE USA, INC. 6529 LEMONT IL
2014-10-13 331-307 0–9 XXXall 10 · 4 holders which blocks → T-MOBILE USA, INC. 6529 LOMBARD IL
2014-10-13 331-980 0–9 XXXwhole prefix which blocks → T-MOBILE USA, INC. 6529 AURORA IL
2014-07-16 331-254 0–9 XXXall 10 · 5 holders which blocks → T-MOBILE USA, INC. 6529 SUGARGROVE IL
2014-05-15 331-801 0–9 XXXall 10 · 4 holders which blocks → TELEPORT COMMUNICATIONS AMERICA, LLC - IL 7136 DOWNERSGRV IL
2014-05-15 331-903 0–9 XXXall 10 · 6 holders which blocks → AT&T ENTERPRISES, LLC 516C DOWNERSGRV IL
2013-10-24 331-703 0–9 XXXall 10 · 4 holders which blocks → T-MOBILE USA, INC. 6529 W CHICAGO 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.