| CoID | Company | Type | Status | States Served | 24X7 Phone |
| CL1OK | Oklahoma 5 LLC - CANCELLED | Wireless/Cellular/PCS | C | | 866-408-6333 |
| CL1TX | MTPCS LLC - CANCELLED | Wireless/Cellular/PCS | C | TX | 866-408-6333 |
| CLARE | Claremont Unified School District | 9-1-1 Admin-CPE ALI | PBX/PS911/Shared Tenant | A | CA | 800-773-7911 |
| CLARO | CLARO ENTERPRISE SOLUTIONS | VoIP Reseller | A | USA - Nationwide | 833-552-5276 |
| CLB | City of Long Beach - CANCELLED | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | C | CA | 562-570-6100 |
| CLDNT | CloudNett | PBX/PS911/Shared Tenant | A | USA - Nationwide | MD | PA | TX | 717-880-4407 |
| CLEAR | ClearConverse Corporation - CANCELLED | VoIP Reseller | C | USA - Nationwide | 559-471-6064 |
| CLEC | Reserve Telecommunications Co. (Cancelled) | Facility | C | LA | 985-536-3635 |
| CLEC1 | Clective GA, Inc. (CANCELLED) | Internet Service Provider | C | GA | 404-272-0445 |
| CLERK | Unnamed Ventures LLC. | VoIP Reseller | A | USA - Nationwide | 415-943-6084 |
| CLHB | Clean Harbors Environmental Services Inc - CANCELLED | CLEC Facility | C | USA | 800-773-7911 |
| CLI | CABLEVISION LIGHTPATH INC. | CLEC Facility | A | CT | NJ | NY | 866-232-5455 |
| CLIPM | Clipper Magazine LLC. - CANCELLED | PBX/PS911/Shared Tenant | C | PA | 717-742-8472 |
| CLKIL | Clarksville Mutual Telephone Co. | Co-OP/Rural | A | IL | 217-822-3677 |
| CLKSD | Clarkston School District J250-185 | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | WA | 509-780-7730 |
| CLMBN | Consolidated Communications of Colorado Company f/k/a Columb | ILEC | A | CO | 916-746-3000 |
| CLNC | Clarence Telephone Company Inc. | Faciltiy | A | IA | 563-452-3852 |
| CLNET | CyberLynk Network LLC | VoIP Reseller | A | USA - Nationwide | 414-858-9335 |
| CLRL | CallRail Inc. | VoIP Provider | A | USA - Nation Wide | 844-489-9700 |
| CLRTK | Cleartalk (Cancelled) | Facility | C | CO | 970-234-9996 |
| CLSIP | ClearSIP Inc. - CANCELLED | VoIP Reseller | C | USA - Nation Wide | 870-569-3442 |
| CLTEL | Clear Lake Independent Telephone Company | Teleco | A | IA | 641-357-2111 |
| CLTO | Celito Communications Inc | VoIP Provider | A | USA - Nation Wide | 919-852-1238 |
| CLU | California Lutheran University - CANCELLED | PBX/PS911/Shared Tenant | C | Thousand Oaks | 805-493-3911 |
| CLV | City of Las Vegas | PBX/PS911/Shared Tenant | A | NV | 702 229-6880 |
| CLW | Coastline Wireless LLC - CANCELLED | PBX/PS911/Shared Tenant Wireless/Cellular/PCS VoIP Provider | C | ME | 207-331-4091 |
| CMAC | Coal-Mac LLC | PBX/PS911/Shared Tenant | A | WV | 314-994-2990 Arch Coal He |
| CMAN | City of Manassas | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) PBX/PS911/Shared Tenant | A | VA | 703-257-8295 |
| CMAV | ComAv Corporation (Out of Business) | Facility | C | NY, MA, ME, RI, NH, VT, NJ, PA | 888-452-6628 |
| CMBR | CAMBRIDGE TELEPHONE COMPANY | CLEC Facility ILEC VoIP Provider | A | IL | 309-944-2103 |
| CMC | CMC Telecom (INACTIVE) | Facility | C | MI | 248-668-2800 |
| CMCH | Cameron Memorial Community Hospital | ILEC | A | IN | 912-373-6572 |
| CMCNH | Catholic Medical Center - CANCELLED | PBX/PS911/Shared Tenant | C | NH | 603-314-7225 |
| CMCS | Cyber Mesa Computer Systems | Facility | A | NM | 505-988-9200 |
| CMCST | Comcast | VoIP Provider | A | USA - Nationwide | 800-777-9824 (option 1) |
| CMHS | Canaan Schools - CANCELLED | PBX/PS911/Shared Tenant | C | VT | 802-266-8910 |
| CML | CML Telephone Cooperative Association | Co-Op/Rural ILEC | A | IA | 712-443-8222 |
| CMMAG | Central Maine Motors Inc | PBX/PS911/Shared Tenant | A | ME | 207-314-0371 |
| CMNT | ATN International / Commnet Wireless | Wireless/Cellular/PCS | A | AZ | CA | CO | MT | NV | NM | ND | OR | TX | UT | WY | 720-733-5360 |
| CMPLS | Communications Plus Inc | Facility | A | WV | 304-983-2211 |
| CMS | Cellular Mobile Systems of St. Cloud (Cancelled) | Wireless | C | MN, Counties Stearns, Sherburn, Benton | 320-292-8450 |
| CMS45 | Cardigan Mountain School | PBX/PS911/Shared Tenant | A | NH | 603-523-3541 |
| CMSCP | ComScape Telecommunications, Inc.(Cancelled) | Facility | C | WV, NC | 561-540-4760 |
| CMTC | Casey Mutual Telephone Co | ILEC | A | IA | 641-740-5034 |
| CMTCC | ComTec Cloud Service Inc | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | USA - Nationwide | 856-691-5111 |
| CMTCH | Comtech Telecommunications Corp. | Database Management System Provider VPC | A | USA - Nationwide | 800-959-3749 |
| CMTEL | Citizens Mututal Telephone Cooperative | Co-Op/Rural | ILEC | PBX/PS911/Shared Tenant | A | IA | 641-664-1000 |
| CMTL | Community Telephone Co Inc | CLEC Facility ILEC VoIP Provider | A | TX | 940-423-6201 |
| CMUPD | Central Michigan University Police Department | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | MI | 989-774-3081 |
| CMWVZ | Midwest Communications dba ComWavz (Cancelled) | Facility | C | OH | 419-367-8440 |