| Colorado Teleserv, Inc. | Rock Solid Broadband | Aurora, CO | Inactive |
| Coltech Enterprise Corp | - | Pembroke Pines, FL | Inactive |
| Columbia Telecommunications, Inc. | - | Baton Rouge, LA | Inactive |
| Columbus 1, 220 SMR (GP) | - | Clinton, MS | Inactive |
| ComExpress Communications, Inc. | ComExpress Communications | Bethesda, MD | Inactive |
| ComScape Telecommunication of Charleston, Inc. | - | West Palm Beach, FL | Inactive |
| ComSouth Telenet, Inc. | - | Hawkinsville, GA | Active |
| Comcast Business Communications, LLC. | Comcast Long Distance | Philadelphia, PA | Active |
| Comcast MH Telephony Communications of Florida, In | - | Moorestown, NJ | Active |
| Comcast Phone II, LLC. | COMCAST DIGITAL PHONE | Philadelphia, PA | Active |
| Comcast Phone of Maryland, Inc. | Comcast Digital Phone | Philadelphia, PA | Inactive |
| Comcast Phone of Michigan, LLC | Comcast Digital Phone | Philadelphia, PA | Active |
| Comcast Phone of New York, LLC. | COMCAST DIGITAL PHONE | Philadelphia, PA | Inactive |
| Comcast Phone of Northern Virginia, Inc. | Comcast Digital Phone of Northern Virginia | Philadelphia, PA | Inactive |
| Comcast Phone, LLC | Comcast Digital Phone | Philadelphia, PA | Active |
| Comcast Telephony Communications of Florida, Inc. | Comcast Telephony Communications of Florida, Inc. | Moorestown, NJ | Inactive |
| Comcast Telephony Communications of Maryland, Inc. | - | Philadelphia, PA | Active |
| Comcast of Northern Maryland, Inc. | Comcast Digital Phone | Philadelphia, PA | Inactive |
| Comlink, LLC. | - | East Lansing, MI | Inactive |
| Comm South Companies of Virginia, Inc. | - | Dallas, TX | Inactive |
| CommChoice of Iowa | - | Sergeant Bluff, IA | Active |
| CommPartners, LLC | - | Las Vegas, NV | Inactive |
| Common Point LLC | - | Chicago, IL | Active |
| Communication Decisions-SNVC, LLC | CDS Telecom | Fairfax, VA | Inactive |
| Communication Impact, Inc. | - | Chico, CA | Inactive |
| Communication Solutions Partners, Inc. | - | Southwick, MA | Inactive |
| Communications Authority Inc | Communications Authority | Lakewood Ranch, FL | Active |
| Communications Buying Group, Inc. | - | Englewood, CO | Inactive |
| Communications Plus, Inc. | - | Morgantown, WV | Active |
| Communications Supply Corporation | - | Carol Stream, IL | Active |
| Communications Venture Corporation | InDigital Telcom | Fort Wayne, IN | Active |
| Communications World of Tulsa, Inc. | Edge Technologies | Tulsa, OK | Inactive |
| Community Cablevision Company | - | Skiatook, OK | Inactive |
| Community Fiber Solutions, Inc. | - | Lima, OH | Active |
| Community Service Long Distance Co. | CommTel | Winthrop, ME | Active |
| CompTech Computer Technologies, Inc. | - | Dayton, OH | Inactive |
| Competitive Communications, Inc. | Competitive Communications, Inc. (CCI) | Riverside, CA | Inactive |
| Computer 5, Inc. | LocalTel Communications | East Wenatchee, WA | Active |
| Computer Network Technology Corp. | - | San Jose, CA | Inactive |
| Computer Techniques, Inc. | CTI Fiber | Taylorville, IL | Active |
| Coms.com, Inc. | - | Germantown, MD | Inactive |
| Comspan Communications, Inc. | ComSpanUSA | Roseburg, OR | Active |
| Concepts Marketing Corporation, Inc. | - | - | Active |
| Conectiv Communications, Inc. | Conectiv Communications | Newark, DE | Inactive |
| Connect Communications, LLC | - | Statesville, NC | Inactive |
| Connect Insured Telephone, Inc. | Connect I.T. | Houston, TX | Inactive |
| Connect Paging, Inc. | - | Fort Worth, TX | Inactive |
| ConnectNow! TeleComm, LLC | - | Columbia, SC | Inactive |
| ConnectTo Communications, Inc. | - | Glendale, CA | Active |
| Connecticut Datanet, LLC | - | Boxborough, MA | Inactive |