Area code
Area code 331 — Aurora, IL
Illinois · in service since October 7, 2007
Area code 331 covers parts of Illinois; the place with the most of its prefixes is Aurora. It is an overlay: 630 serves the same area, so neighbors can have different area codes.
Overlay, same area: 630
Local time in Aurora
Spam reports from Sep 23 – Oct 22, 2026
Average #168 of 461 codes
548 FTC complaints
Consumer reports, not verified by the FTC.
See the reports- Time zoneCentral Time
- Local calls1 + 10 digits
- Prefixes239 assigned
- Runs out~1Q 2080
- Unwanted call?Block & report
Spam call reports about 331 numbers
Complaints by week
Sep 11 – Oct 22, 2026Show as table
| Week starting | Complaints |
|---|---|
| Sep 7 (3 days) | 22 |
| Sep 14 | 82 |
| Sep 21 | 64 |
| Sep 28 | 92 |
| Oct 5 | 140 |
| Oct 12 | 216 |
| Oct 19 (4 days) | 64 |
Compared with all codes
- Robocalls
- 80%all codes 75%
- Callers with the same code
- 3%all codes 35%
- Rank by complaints
- #168of 461 · middle half
- FCC complaints, Oct 2025 – Sep 2026
- 427 about text messages
What the calls were about
Sep 11 – Oct 22, 2026
| Subject | Complaints | |
|---|---|---|
| Reducing your debt (credit cards, mortgage, student loans) | 289 42% | |
| Calls pretending to be government, businesses, or family and friends | 56 8% | |
| Dropped call or no message | 29 4% | |
| Home improvement & cleaning | 12 2% | |
| Medical & prescriptions | 6 1% | |
| Energy, solar, & utilities | 2 <1% |
Where the people who complained live
Sep 11 – Oct 22, 2026
| State | Complaints | |
|---|---|---|
| Illinois | 195 29% | |
| California | 92 14% | |
| Florida | 42 6% | |
| Virginia | 36 5% | |
| New Jersey | 29 4% |
October 2026 (partial) report · most reported
Consumer reports, not verified by the FTC · source
Source: FTC Do Not Call complaints created Sep 11 – Oct 22, 2026. They are reported by consumers and are not verified by the FTC; caller ID can be spoofed (how we count).
Source: FCC Consumer Complaints data, unwanted calls filed Oct 1, 2025 – Sep 30, 2026, by caller ID; not verified by the FCC.
Area code 331 location and prefixes
| Exchange (NANPA) | Place | County | Prefixes |
|---|---|---|---|
| AURORA | Aurora | spans 4 counties | 45 |
| NAPERVILLE | Naperville | spans 2 counties | 33 |
| DOWNERSGRV | Downers Grove | DuPage County | 21 |
| ST CHARLES | St. Charles | spans 2 counties | 18 |
| LOMBARD | Lombard | DuPage County | 13 |
| ELMHURST | Elmhurst | spans 2 counties | 10 |
| LEMONT | Lemont | spans 3 counties | 10 |
| BARTLETT | Bartlett | spans 3 counties | 8 |
| W CHICAGO | West Chicago | DuPage County | 8 |
| WHEATON | Wheaton | DuPage County | 8 |
Plus 14 smaller exchange areas.
Source: NANPA CO codes of Oct 23, 2026; places: U.S. Census Bureau, matched by DialWhere (how).
NANPA record
- Location
- Illinois
- Assigned by NANPA
- July 23, 1999
- Local dialing
- 1 + 10 digits (NANPA: 1+10D)
- NANPA planning letters
- PL-362, PL-357, PL-195
Source: NANPA, NPA database of Oct 24, 2026.
Is 331 running out of numbers?
Previous forecast (October 2025): 2073, moved later by 7 years.
Forecast exhaust year by edition
Source: NANPA NRUF forecast, April 2026 edition.
Who holds 331 prefixes
The five largest of 27 original holders
As listed by NANPA, not today’s carrier.
| Holder (as listed) | Prefixes | |
|---|---|---|
| T-Mobile USA, Inc. | 42 18% | |
| Onvoy, LLC | 39 16% | |
| Verizon Wireless | 33 14% | |
| New Cingular Wireless PCS, LLC | 26 11% | |
| Fractel, LLC | 18 8% |
Source: NANPA CO codes of Oct 23, 2026.
Questions about area code 331
What area code is 331?
An Illinois area code, in service since October 7, 2007.
Where is 331 area code, and what time zone is it in?
Aurora, IL; Central Time.
Why am I getting spam calls from 331?
548 FTC complaints from Sep 23 – Oct 22, 2026, most often about debt reduction (not verified by the FTC; caller ID can be spoofed).
Will 331 get a new area code?
NANPA forecasts exhaust in 1Q 2080; no relief planning listed.