Area code 312 is assigned for use in Illinois since Jan 01, 1947. View all phone prefixes used in area code 312 or other area codes in Illinois. Included with the location of each prefix are the phone companies / service providers that operates them.
| Area code / prefix | Location | Company / Service Provider |
|---|---|---|
| 312-200 | CHICAGO, IL | METROPCS, INC. |
| 312-201 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-202 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-203 | CHICAGO, IL | NEW CINGULAR WIRELESS PCS, LLC - IL |
| 312-204 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-205 | CHICAGO, IL | MCIMETRO ACCESS TRANSMISSION SERVICES LLC |
| 312-206 | CHICAGO, IL | NEW CINGULAR WIRELESS PCS, LLC - IL |
| 312-207 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-208 | CHICAGO, IL | NEW CINGULAR WIRELESS PCS, LLC - IL |
| 312-209 | NORTHBROOK, IL | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL |
| 312-210 | CHICAGO, IL | PEERLESS NETWORK OF ILLINOIS, LLC - IL |
| 312-212 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-213 | CHICAGO, IL | NEW CINGULAR WIRELESS PCS, LLC - IL |
| 312-214 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-215 | WHEELING, IL | NEW CINGULAR WIRELESS PCS, LLC - IL |
| 312-216 | CHICAGO, IL | FIRST COMMUNICATIONS, LLC - IL |
| 312-217 | CHICAGO, IL | T-MOBILE USA, INC. |
| 312-218 | CHICAGO, IL | NEW CINGULAR WIRELESS PCS, LLC - IL |
| 312-219 | CHICAGO, IL | BANDWIDTH.COM CLEC, LLC - IL |
| 312-220 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-221 | CHICAGO, IL | T-MOBILE USA, INC. |
| 312-222 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-223 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-224 | CHICAGO, IL | LEVEL 3 COMMUNICATIONS, LLC - IL |
| 312-225 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-226 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-227 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-228 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-229 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-230 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-231 | ROSELLE, IL | NEW CINGULAR WIRELESS PCS, LLC - IL |
| 312-232 | CHICAGO, IL | AMERICAN MESSAGING SERVICES, LLC |
| 312-233 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-234 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-235 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-236 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-237 | CHICAGO, IL | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL |
| 312-238 | CHICAGO, IL | LEVEL 3 COMMUNICATIONS, LLC - IL |
| 312-239 | CHICAGO, IL | AT&T - LOCAL |
| 312-240 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-241 | CHICAGO, IL | NEW CINGULAR WIRELESS PCS, LLC - IL |
| 312-242 | CHICAGO, IL | TELEPORT COMMUNICATIONS AMERICA, LLC - IL |
| 312-243 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-244 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-245 | CHICAGO, IL | ILLINOIS BELL TEL CO |
| 312-246 | WHEELING, IL | NEW CINGULAR WIRELESS PCS, LLC - IL |
| 312-247 | CHICAGO, IL | FIRST COMMUNICATIONS, LLC - IL |
| 312-248 | CHICAGO, IL | METROPCS, INC. |
| 312-249 | CHICAGO, IL | USA MOBILITY WIRELESS, INC. |
| 312-250 | CHICAGO, IL | USA MOBILITY WIRELESS, INC. |
| 312 Area Code Information | ||
|---|---|---|
| Type of code: | General Purpose Code | |
| Location: | IL - US | |
| Time zone: | C | |
| Assigned for use: | Yes | |
| Code in service: | Yes | |
| Service date: | 01/01/47 | |
| In jeopardy: | No | |
| Relief in progress: | No | |
| NPA Relief status: | ||
| Code assignable: | Yes | |
| Geographic or non-geographic: |
G | |
| Reserved for future use: | No | |
| Planning letter(s): | 392 390 195 | |
| Overlay code: | Yes | |
| Overlay complex: | 312/872 | |
| Dialing plan | Standard | Permissive |
| Home local calls: | 1+10D | NA |
| Foreign local calls: | 1+10D | NA |
| Home toll calls: | 1+10D | NA |
| Foreign toll calls: | 1+10D | - |