331 Area Code: Aurora, Illinois
Area code 331 serves Aurora, Naperville and Downers Grove, Illinois in the Central time zone, in service since 2007. Consumers have filed 2,048 unwanted-call complaints against 1,269 different 331 numbers, 495 of them with the FTC in the last 30 days. Look up the exact number that called you below.
Area code 331 at a glance
- State
- Illinois
- Main cities
- Aurora, Naperville, Downers Grove, St. Charles, Lombard, Lemont + 18 more
- Counties
- DuPage County, Kane County, Kendall County, Cook County
- Local time
- —Central
- In service since
- October 7, 2007
- Overlay of
- 630
- Local dialing
- 10 digits (area code + number)
- Exchanges
- 24 rate centers, 224 prefixes
Sources: NANPA area code and central office code records (refreshed weekly); cities and counties matched from US Census Bureau and USGS place names.
Most-reported 331 numbers
Ranked by FTC Do Not Call complaints this month, then all-time FTC and FCC complaints. Only numbers with enough complaints for a full report page are listed. Click one for what it was reported for and where.
- (331) 888-1940Debt reduction246 this month2026-10-15
- (331) 342-3003Dropped call / no message1 this month2026-10-09
- (331) 888-1773Debt reduction152 reports2026-09-16
- (331) 888-1953Debt reduction17 reports2026-08-15
- (331) 888-1662Debt reduction16 reports2026-09-02
- (331) 888-1948Debt reduction14 reports2026-09-13
- (331) 248-4967Debt reduction12 reports2026-09-02
- (331) 342-3011Impostor (government, business, family)10 reports2026-09-15
What calls from 331 numbers are about
1,190 FTC Do Not Call complaints about 331 numbers since Jul 24. The most common named subject is debt-relief pitches, at 38% of complaints (90% of those were recorded messages). Overall, 76% of callers who answered said the call was a robocall.
FTC complaint subjects
- Debt reduction45738%
- Other / unspecified41835%
- Impostor (government, business, family)1008%
- No subject given807%
- Dropped call / no message676%
- Home improvement & cleaning313%
- Warranties & protection plans81%
FCC complaints by call type, last 2 years
- Live Voice4251%
- Prerecorded Voice2935%
- Text Message1214%
14% of recent FCC complaints about 331 numbers are about text messages, not calls.
When 331 spam calls come in
30% of complaints that give a call time describe calls between 11am and 2pm. 92% came Monday to Friday, most on Fridays, the pattern of call-center robocall campaigns that run on business hours. Times are as consumers reported them to the FTC.
By hour of the day
By day of the week
Is it getting worse?
521 FTC complaints about 331 numbers in the last four weeks, up 51% on the four weeks before. FCC complaints about 331 numbers peaked in 2018 (136); the FTC's daily Do Not Call data has carried most of the volume since mid-2026.
FTC complaints per week
FCC complaints per year
Years shown as '15 to '26; the current year is partial.
Who gets these calls
Only 33% of the FTC complaints about 331 numbers came from Illinois residents; the most came from California, Florida and Virginia. 331 numbers are being used for nationwide campaigns, so the area code says little about where the caller is.
Where complainants live
- Illinois38833%
- California13511%
- Florida797%
- Virginia524%
- New Jersey454%
What people with 331 numbers report
People whose own number starts with 331 filed 100 FTC complaints since Jul 24. 39% were about calls showing another 331 number. The most common named subject was debt-relief pitches.
Area codes on the calls they reported
- 331 (same code)3939%
- 63066%
- 877 (toll-free)55%
- 57044%
- 833 (toll-free)44%
Likely campaigns using 331 numbers
Groups of numbers that drew the same FTC complaint in the same pattern over the last 60 days. The grouping is statistical and doesn't identify who is calling.
Busiest 331 prefixes this month
FTC complaints in the last 30 days, grouped by the first six digits. When one prefix collects complaints about many different numbers, a campaign is usually cycling through that block. The carrier is who NANPA assigned the prefix to, not who made the calls.
| Prefix | Complaints | Numbers | Carrier | Exchange |
|---|---|---|---|---|
| (331) 888-xxxx | 255 | 6 | Peerless Network | Warrenville |
| (331) 356-xxxxcampaign | 19 | 19 | Fractel, LLC | Bartlett |
| (331) 342-xxxx | 15 | 15 | Verizon Wireless (Cellco Partnership) | Naperville |
| (331) 296-xxxx | 15 | 14 | Boost Subscriberco L.L.C. | Wheaton |
| (331) 202-xxxx | 14 | 14 | T-Mobile USA | Elmhurst |
Carriers operating in 331
NANPA has assigned 224 331 prefixes (NPA-NXX central-office codes) across 24 rate centers: 46% to wireless carriers, 54% to landline and VoIP operators; 100% are pooled blocks shared by several carriers. 6 prefixes were assigned in the last 12 months (newest 2026-08-14). The carrier holding a prefix is who the number was issued through. It says nothing about who is calling, since caller ID is routinely spoofed.
| Carrier | Type | Prefixes | Rate centers | Newest assignment |
|---|---|---|---|---|
| T-Mobile USA | Wireless | 42(19%) | 11 | 2022-08-12 |
| Onvoy (Sinch) | Competitive / VoIP (CLEC) | 39(17%) | 17 | 2026-07-28 |
| Verizon Wireless (Cellco Partnership) | Wireless | 33(15%) | 5 | 2026-05-18 |
| AT&T Mobility (New Cingular Wireless PCS) | Wireless | 26(12%) | 6 | 2026-08-14 |
| Fractel, LLC | Competitive / VoIP (CLEC) | 18(8%) | 14 | 2021-10-27 |
| Bandwidth.com | Competitive / VoIP (CLEC) | 11(5%) | 10 | 2022-07-20 |
| Ton80 Communications, LLC | Competitive / VoIP (CLEC) | 9(4%) | 9 | 2022-02-25 |
| Level 3 (Lumen) | Competitive / VoIP (CLEC) | 6(3%) | 6 | 2020-03-06 |
| Onvoy (Sinch) | Competitive / VoIP (CLEC) | 5(2%) | 4 | 2025-01-29 |
| Peerless Network | Competitive / VoIP (CLEC) | 5(2%) | 5 | 2013-04-10 |
| Comcast (Xfinity Voice) | Competitive / VoIP (CLEC) | 4(2%) | 4 | 2016-01-04 |
| MCImetro (Verizon Business) | Competitive / VoIP (CLEC) | 4(2%) | 3 | 2017-11-07 |
Largest rate centers (exchanges) by prefixes: Aurora (45), Naperville (33), Downers Grove (21), St. Charles (18), Lombard (13), Elmhurst (10), Lemont (10), Bartlett (8), West Chicago (8), Wheaton (8). Source: NANPA Central Office Code Utilized Assignments (public, refreshed weekly).
What to do about calls from 331 numbers
Before you call back
- Debt reduction is the top named complaint here. Don't pay upfront fees for debt relief; the FTC's Telemarketing Sales Rule bans them. Talk to your lender or a nonprofit credit counselor instead. Read about debt-relief robocalls.
- Look up the full number above. A missed call from 331 with no voicemail is usually a robocall; anyone who needs you will leave a message.
- Block repeat callers: iPhone, Android, or your carrier's free filter (Verizon, AT&T, T-Mobile).
Report it in Illinois
- Unwanted sales calls and robocalls: donotcall.gov (FTC). Scams and fraud: ReportFraud.ftc.gov.
- Spoofing, texts and call-blocking problems: FCC consumer complaints.
- State complaints: Illinois Attorney General.
- Illinois formally adopted the FTC's National Do Not Call Registry as its own state list rather than running a separate one, so a single free registration at donotcall.gov covers you. State authorities can still enforce against telemarketers who ignore it, in addition to any federal penalty.
Your FTC and FCC reports are published (without your name or number) in the datasets this page is built from. How to report unwanted calls.
Area code 331: questions answered from the data
Where is area code 331?
Area code 331 serves Aurora, Naperville and Downers Grove, Illinois, covering DuPage County, Kane County and Kendall County and 1 more county. It has been in service since October 7, 2007.
What time zone is area code 331 in?
Area code 331 is in the Central time zone (UTC−6, or UTC−5 during daylight saving time). The current local time is shown at the top of this page.
What are calls from 331 numbers usually about?
Since Jul 24, consumers filed 1,190 FTC Do Not Call complaints about 331 numbers. The most common named subject was debt-relief pitches: 38% of complaints, 90% of them recorded messages. Across all subjects, 76% of callers who answered the question said the call was a robocall.
When do 331 spam calls happen?
30% of the complaints that give a call time describe calls between 11am and 2pm, and 92% came on weekdays, most often on Friday. Times are as consumers reported them.
Are calls from 331 numbers really local?
Not necessarily. Only 33% of the FTC complaints about 331 numbers came from Illinois residents; the most came from California, Florida and Virginia. 331 numbers are being used for nationwide campaigns, so the area code says little about where the caller is.
Are 331 robocalls increasing?
In the four weeks to Oct 15, consumers filed 521 FTC complaints about 331 numbers, 51% more than the four weeks before.
How do I report a 331 scam call in Illinois?
Report unwanted sales calls and robocalls to the FTC at donotcall.gov, and scams to ReportFraud.ftc.gov. The FCC takes complaints at consumercomplaints.fcc.gov. In Illinois, the Illinois Attorney General also handles consumer complaints about scam calls. Reports feed the public data this page is built from.
Overlay and nearby area codes
Sources: FTC Do Not Call complaints (unverified consumer reports), published every weekday and available here from Jul 24; FCC Consumer Complaint Data, public record, imported nightly; NANPA numbering records. A number appearing here means consumers reported calls that displayed it. Caller ID can be spoofed.