Skip to content
Before You Call Back

Area code 331

Area code 331 serves Illinois, including Aurora, Naperville and Downers Grove (Central time). It has been in service since October 7, 2007 and shares its area with 630.

Numbers starting with 331 drew 1,213 reports to the FTC from Aug 14, 2026 to Nov 11, 2026 and 450 complaints to the FCC since November 2023. The number on your screen can be faked, so a 331 number proves nothing about where a call came from.

Location
IllinoisChicago-Naperville-Elgin, IL-IN Metropolitan Statistical Area
Time zone
Central
In service since
October 7, 2007Created from 630
Overlay
Same area as 630
Local calls
Dial 1 + 10 digits
Exchanges in use
225 of 792held by 25 carriers
Projected to run out
4Q 2087NANPA forecast 2026.2

Complaints about 331 numbers

Reports where the number on the consumer's caller ID (or, for the FCC, the number the caller asked them to call back) starts with 331. These are counts of what people reported; the agencies do not verify them.

FTC reports, Aug 14, 2026 to Nov 11, 2026

1,213

FCC complaints since November 2023

450

Different 331 numbers reported

997

FCC complaints naming a 331 number, by month

November 2023 to October 2026. Source: FCC Consumer Complaints Data.

Show as a table
MonthComplaints
November 202319
December 202311
January 202418
February 202411
March 20246
April 20245
May 202412
June 202410
July 20244
August 20248
September 20246
October 202410
November 20247
December 20245
January 20258
February 20252
March 20256
April 20258
May 20257
June 202510
July 20255
August 20255
September 20254
October 20251
November 20251
December 20255
January 20266
February 20265
March 20265
April 20262
May 20263
June 202612
July 2026106
August 202621
September 202628
October 202665

What people said 331 calls were about

Subjects picked in FTC reports, August 14, 2026 to November 11, 2026. 863 of 1,213 reports were robocalls.

Show as a table
SubjectReports
Reducing your debt (credit cards, mortgage, student loans)475
Other443
Calls pretending to be government, businesses, or family and friends95
Dropped call or no message69
Home improvement and cleaning22
Warranties and protection plans9

Most reported 331 numbers

Numbers with at least five reports from three or more places in the last twelve months. Many of them are likely spoofed.

Places served by 331

NANPA lists 24 rate centers for 331. A rate center is the town or district a block of numbers is tied to for billing; sorted here by how many exchanges each holds.
  • Aurora45
  • Naperville33
  • Downers Grove21
  • Saint Charles18
  • Lombard13
  • Elmhurst10
  • Lemont10
  • Bartlett8
  • West Chicago8
  • Wheaton8
  • Geneva7
  • Hinsdale7
  • Oswego7
  • Sugar Grove6
  • Yorkville4
  • Elburn3
  • Glen Ellyn3
  • Itasca3
  • Batavia2
  • Big Rock2
  • Kaneville2
  • Plano2
  • Warrenville2
  • Roselle1

Phone companies holding 331 exchanges

Each exchange (the three digits after the area code) is assigned to one carrier. 100% of these exchanges are pooled: their numbers are handed out in blocks of 1,000 to other carriers, so the holder below is not always the company serving a given number.

Exchanges held, top 8 of 25 carriers

NANPA central office code assignments, file of November 11, 2026.

Show as a table
Carrier (legal name)Exchanges
T-Mobile USA, Inc.42
Onvoy, LLC40
Cellco Partnership dba Verizon Wireless - IL33
New Cingular Wireless PCS, LLC - IL26
Fractel, LLC18
Bandwidth.com CLEC, LLC - IL11
Ton80 Communications, LLC9
Level 3 Communications, LLC - IL6

When today's 331 exchanges were assigned

Exchanges still assigned, by year of assignment. Exchanges returned since are not counted.

Show as a table
YearExchanges
20079
200814
20093
20106
201111
201212
20139
201410
201511
201613
201714
20186
201910
20209
202121
202220
202312
202412
20257
20265

Check a 331 number

A check shows the carrier and rate center of the number's exchange and every FTC and FCC report about that exact number. Why the number on screen can be fake.

Other area codes in Illinois

NANPA area code database and central office code file of November 11, 2026; FCC complaints November 1, 2023 to November 11, 2026; FTC reports August 14, 2026 to November 11, 2026. How the data is used.

Official sources (7)Show