| CoID | Company | Type | Status | States Served | 24X7 Phone |
| XCY | CMN-RUS Inc. f/k/a Cinergy MetroNet | CLEC Facility | A | IN | 877-407-3224 |
| XENOI | IONEX (Cancelled) | Facility | C | TX, KS, OK, MO | 877-333-2555 |
| XGSG | XG Service Group | VoIP Reseller VoIP Provider | A | USA - Nationwide | 734-245-4100 |
| XIT | XIT Communications | Facility | A | TX | 806-384-3311 |
| XITC | XIT Cellular - CANCELLED | Wireless/Cellular/PCS | C | TX | 806-384-3311 |
| XNW | nWire / TNCI Operating Company - CANCELLED | CLEC Facility CLEC Reseller VoIP Reseller VoIP Provider | C | USA - Nation Wide | 800-511-9048 |
| XOBEE | Xobee Networks Inc. - CANCELLED | VoIP Provider | C | USA - Nationwide | 5594902800 opt. 1 |
| XOP | Opextel LLC - CANCELLED | CLEC Facility | CLEC Reseller | CLE UNE | VoIP Provider | C | FL | 786-693-8331 |
| XOV | Voxline Networks - CANCELLED | VoIP Reseller | C | USA - Nation Wide | 646-556-7314 |
| XOXO | Verizon | CLEC Facility | A | USA - Nationwide | 800-483-0911 |
| XPC | Xspedius Corp. (Cancelled - See ACSI) | Facility | C | LA, MS, AL, FL, TN, NC | 877-322-0414 |
| XPT | eXpeTel Communications (CANCELLED) | Facility | C | MS | 800-310-4481 |
| XTEL | Xtel Communications Inc - CANCELLED | CLEC Facility | C | USA | 856-596-4000 |
| XTEX | Crosstex Energy Services L.P. | PBX | A | USA | 214-721-9496 |
| YAHOO | YaHoo!, Inc. (Cancelled) | PBX | C | ALL | 800-464-4402 |
| YALE | Yale University | PBX | A | CT | 203-785-4171 |
| YATES | Yates County Buildings & Grounds - CANCELLED | PBX | C | OTHER | 315-536-4438 |
| YCC | Yucca Communications | CLEC Facility | A | NM | 575-226-2255 |
| YCI | West Kentucky Rural Telephone Cooperative (INACTIVE) | Wireless/Celluar/PCS | C | TN | 731-643-6121 |
| YCJUS | YCJUSD | PBX/PS911/Shared Tenant | | CA | (909) 797-0174 |
| YCOM | Consolidated Communications of Washington Company f/k/a YCOM | ILEC | A | WA | 916-746-3000 |
| YCOR | Yamhill County | PBX/PS911/Shared Tenant | A | OR | 503-434-7505 |
| YCTC | Arkwest Communications | Facility | A | AR | 479-495-3113 |
| YELCO | Yelcot | Cable Digital CLEC Facility ILEC VoIP Provider | A | AR | 870-449-6600 |
| YHOSP | York Hospital | PBX/PS911/Shared Tenant | A | ME | NH | 207-363-4321 |
| YMESD | Yarmouth School Department | PBX/PS911/Shared Tenant | A | ME | 207-846-3333 |
| YMHIL | Yamhill Communications Agency (CANCELLED) | 9-1-1 Admin-CPE ALI | C | Yamhill County, OR | 503-464-6500 |
| YMX | Ymax Communications Corp | CLEC Reseller | A | USA - Nationwide | 800-357-4911 |
| YOJI | Yoji Inc. - CANCELLED | VoIP Provider | C | CA | 213-537-8280 |
| YOURS | YourSip Telecom | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | USA - Nationwide | 727-450-8200 |
| YPE | VoIP PBX Express.Cloud LLC | VoIP Reseller VoIP Provider | A | USA - Nationwide | 206-966-1092 |
| YTC | West Kentucky Rural Telephone Cooperative (INACTIVE) | Wireless/Cellular/PCS | C | TN | 731-643-6121 |
| YTCI | Yeoman Telephone Company Inc. | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | IN | 574-965-2100 |
| YTL | Y Tell, Inc. (Cancelled) | CLEC Facility | C | NY | 646-372-7088 |
| YTNJ | Yorktel Telecom | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | USA - Nationwide | 786-381-8888 |
| YVFWC | Yakima Valley Farm Workers Clinics | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | OR | WA | 509-865-7861 |
| YVS | PBT d/b/a Comporium Communications | CLEC Facility VoIP Provider | A | SC | 803-326-7370 |
| YVT | Yadkin Valley Telecom Inc | CLEC Facility | A | NC | 336-463-5047 |
| YVTMC | Yadkin Valley Telephone | ILEC | A | NC | 336-463-5047 |
| YWTCO | Yukon-Waltz Telephone Company | ILEC | A | PA | 724-722-1110 |
| ZAN | Zan Inc. - CANCELLED | VoIP Provider | C | FL | 954-804-0462 |
| ZEER | The One and Only Corp - CANCELLED | VoIP Provider | C | USA - Nationwide | 650-250-6694 |
| ZELLA | Zella Technologies LLC | VoIP Provider | A | USA - Nationwide | 985-520-4824 |
| ZEN | Zen Communications | VoIP Reseller VoIP Provider | A | CO | NM | UT | 970-232-2120 |
| ZENDA | Zenda Telephone Company Inc. | ILEC | A | KS | 620-243-4924 |
| ZENK | ZENK Group d/b/a Planet Access (CANCELLED) | Facility/Reseller | C | MI | 800-500-6140 |
| ZHILL | City of Zephyrhills | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | FL | 813-780-0046 |
| ZIP | Zip911 | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | A | USA - Nationwide | 844-700-4141 |
| ZIPPY | ZippyTech Inc. | CLEC Facility | A | CO | 970-385-2500 |
| ZLINY | New Marketing Group Inc | VoIP Reseller VoIP Provider | A | USA - Nation Wide | 516-435-8777 |