| CoID | Company | Type | Status | States Served | 24X7 Phone |
| CARLS | Carlsbad by the Sea - CANCELLED | PBX | C | All | 480-719-8556 |
| CARNT | Carnegie Telephone Co. Inc | ILEC | A | OK | 580-654-1002 |
| CARO | Carolina Phone (Out of Business) | Wireless | C | SC | 864-599-7820 |
| CARR | Carr Telephone Company | ILEC | A | MI | 231-898-4400 |
| CARSL | Carousel Industries Inc. | VoIP Reseller | A | USA - Nationwide | 866-408-4596 |
| CARSO | Carson Communications dba Rainbow Communications | Cable Digital | CLEC Facility | CLEC Reseller | A | KS | 785-548-7511 |
| CARTC | Carr Telephone Company | CLEC Facility | A | MI | 231-898-4400 |
| CASC | CAS Communications LLC | CLEC Facility | A | WV | 304-420-2470 |
| CASD | Coatesville Area School District(Cancelled) | CLEC Facility | C | Coatesville, PA | 484-576-0989 |
| CASS | Consolidated Communications of Missouri Company | ILEC | A | KS | MO | 916-746-3000 |
| CAST | Castleton State College | PBX/PS911/Shared Tenant | A | Castleton State College Campus | 802-468-5611 |
| CASTL | Cass Telephone Company | ILEC | A | USA - Nation Wide | 217-452-3022 |
| CATEL | Cass Telephone Company (Out of Business) | LEC | C | IL | 217-452-3028 |
| CATL | California Telecom - CANCELLED | | C | USA | 213-270-1350 |
| CATT | Native Network Inc. | CLEC Facility | A | ID | OR | WA | 877-857-2288 x2 |
| CAUNE | AT&T California (formerly SBC Pacific Bell) - CANCELLED | CLEC UNE | C | CA | 800-275-0014 |
| CAV | Cavalier Telephone | CLEC Facility | A | DE | DC | MD | NJ | PA | VA | 800-200-1989 option 3 |
| CAVAL | Fort Baker Retreat Group - CANCELLED | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | C | CA | 415-686-9787 |
| CB101 | Code Blue Corporation | PBX/PS911/Shared Tenant VoIP Provider | A | USA - Nationwide | 616-636-7035 |
| CBAD | Cincinnati Bell Any Distance - CANCELLED | CLEC Facility | CLEC Reseller | CLEC UNE | C | USA | 513-397-7326 |
| CBC | Comcast Business Communications Inc. - CANCELLED | CLEC Facility | C | MA | PA | DE | NJ | 800-839-6707 |
| CBCBH | CBC Broadband Holdings, LLC(Inactive) | Cable Digital, CLEC Facility, VoIP Provider | C | CA | 323-908-1317 |
| CBCWA | Columbia Basin College | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | WA | 509-542-4777 |
| CBI | Constellation Brands Inc. | PBX/PS911/Shared Tenant | A | UT | 585-364-4002 |
| CBIT | CBIT Inc. | VoIP Provider | A | WA | 509-578-5424 |
| CBKS | US Army War College | PBX/PS911/Shared Tenant | A | PA | 717-245-3131 |
| CBL | Cooper B-Line - CANCELLED | ILEC | C | IL | 618-407-8297 |
| CBM | CBM Technology - CANCELLED | VoIP Reseller | C | LA | 337-233-5010 |
| CBS | CBS Corp(Inactive) | PBX/PS911/Shared Tenant | C | NY | 212-975-2811 |
| CBT | Cebridge Telecom (Cancelled) | Cable Digital, VoIP | C | TX,CA,LA,MO,OK,VA,WV,NC | 903-939-9008 |
| CBTC | Corn Belt Telephone | ILEC | A | IA | 712-664-2221 |
| CBURY | Canterbury School | PBX/PS911/Shared Tenant | A | CT | 860-210-3800 |
| CBW | Cincinnati Bell Wireless - CANCELLED | Wireless/Celluar/PCS | C | OH | IN | KY | 513-566-3100 |
| CBYND | Cbeyond Communications | CLEC UNE | A | GA | TX | CO | IL | CA | MI | MN | 866-424-9233 |
| CC52 | Coleman County Telephone | ILEC | A | TX | 325-348-3124 |
| CC715 | Sutter Health | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | USA - Nationwide | CA | UT | 916-363-2233 |
| CC911 | Colorado College | PBX/PS911/Shared Tenant | A | CO | 719-389-6707 |
| CCAIN | Clarity Communications Advisors | VoIP Provider | A | USA - Nationwide | 248-327-4309 |
| CCART | Cornish College of the Arts | PBX/PS911/Shared Tenant | A | WA | 206-726-5092 |
| CCAS | Cross Country Automotive Services - CANCELLED | PBX | C | ALL | 800-824-6678 |
| CCBC | The Community College of Baltimore County | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | MD | 443-840-1111 |
| CCBCP | Community College of Beaver County | PBX/PS911/Shared Tenant | A | PA | 724-480-3555 |
| CCBL | Cross Cable Television LLC | CLEC Facility PBX/PS911/Shared Tenant VoIP Provider | A | OK | 918-463-2921 |
| CCC | Citizens Communications Corporation | CLEC Facility | A | VA | 540-745-2111 |
| CCC3 | Cloud Computing Concepts LLC | VoIP Provider | A | USA - Nationwide | 877-247-4949 |
| CCCC | Coastal Carolina Community College - CANCELLED | VoIP Provider | C | NC | 910-455-1221 |
| CCCMD | Carroll Community College(Cancelled) | PBX/PS911/Shared Tenant | C | MD | 410-386-8060 |
| CCCOM | CC Communications | ILEC VoIP Reseller | A | NV | 775-315-5158 |
| CCG | Campus Communications Group Inc. | CLEC | PBX | A | FL | MN | TX | 888-472-8568 |
| CCG1 | Chesterfield County Government | PBX/PS911/Shared Tenant | VoIP | A | VA | 804-796-7127 |