| 01428 21 | TelNG Limited | 27/02/2007 |
| 01428 22 | Localphone Limited | 04/05/2007 |
| 01428 231 | Barritel Limited | 16/11/2011 |
| 01428 232 | Barritel Limited | 16/11/2011 |
| 01428 233 | Barritel Limited | 16/11/2011 |
| 01428 234 | Barritel Limited | 16/11/2011 |
| 01428 235 | Barritel Limited | 16/11/2011 |
| 01428 236 | Barritel Limited | 16/11/2011 |
| 01428 238 | Barritel Limited | 16/11/2011 |
| 01428 239 | Barritel Limited | 16/11/2011 |
| 01428 24 | Redcentric Solutions Limited | 05/06/2015 |
| 01428 26 | TTNC Limited | 11/11/2013 |
| 01428 287 | TalkTalk Communications Limited | 31/08/2011 |
| 01428 288 | TalkTalk Communications Limited | 31/08/2011 |
| 01428 289 | TalkTalk Communications Limited | 31/08/2011 |
| 01428 290 | Resilient PLC | 12/09/2011 |
| 01428 299 | Resilient PLC | 12/09/2011 |
| 01428 30 | (AQ) LIMITED | 11/09/2012 |
| 01428 31 | VoIP-Un Limited | 29/10/2007 |
| 01428 32 | Digital Space Group Limited | 30/11/2007 |
| 01428 33 | Voiceflex Limited | 03/12/2007 |
| 01428 340 | Voxbone SA | 05/12/2011 |
| 01428 35 | Nationwide Telephone Assistance Ltd | 10/07/2008 |
| 01428 36 | Telecom2 Limited | 11/09/2009 |
| 01428 37 | Nodemax Limited | 15/07/2008 |
| 01428 388 | TalkTalk Communications Limited | 08/02/2013 |
| 01428 400 | Dark Group Limited | 11/05/2011 |
| 01428 404 | Dark Group Limited | 11/05/2011 |
| 01428 41 | Solutios Limited | 08/10/2008 |
| 01428 427 | Digital Space Group Limited | 15/03/2016 |
| 01428 43 | Mars Communications Limited | 12/02/2009 |
| 01428 444 | Net-Work Internet Ltd | 10/08/2011 |
| 01428 45 | IPV6 Limited | 04/02/2009 |
| 01428 464 | Andrews & Arnold (Numbers) Ltd | 07/09/2011 |
| 01428 47 | Telecoms World PLC | 13/03/2009 |
| 01428 48 | Sky UK Limited | 02/07/2013 |
| 01428 49 | Nexus Telecommunications Limited | 11/06/2009 |
| 01428 50 | FleXtel Limited | 26/10/2005 |
| 01428 52 | Citrus Telecommunications Ltd | 11/04/2006 |
| 01428 550 | Invoco Ltd | 22/09/2011 |
| 01428 551 | Hello Telecom (UK) Limited | 10/11/2011 |
| 01428 552 | Internexus Networks Limited | 21/11/2011 |
| 01428 553 | API Telecom Limited | 29/03/2012 |
| 01428 554 | Minotaur Telecom Limited | 04/02/2013 |
| 01428 555 | VoiceHost Limited | 22/06/2010 |
| 01428 557 | ICC Networks Ltd | 13/04/2012 |
| 01428 558 | Ziron Limited | 30/07/2012 |
| 01428 559 | Bicom Systems EURL | 02/03/2012 |
| 01428 567 | Spitfire Network Services Limited | 21/07/2011 |
| 01428 57 | Syntec Limited | 18/11/2005 |
| 01428 580 | Number Services Ltd. | 22/11/2018 |
| 01428 581 | Colt Technology Services | 13/08/2018 |
| 01428 582 | Invosys Limited | 23/08/2017 |
| 01428 583 | 24 SEVEN CLOUD COMMUNICATIONS LTD | 17/01/2020 |
| 01428 584 | Club Communications Ltd | 03/07/2018 |
| 01428 585 | Adepteo Limited | 17/01/2017 |
| 01428 586 | Zapappi Ltd | 05/01/2018 |
| 01428 587 | Belgacom International Carrier Services SA | 03/02/2020 |
| 01428 588 | I.T Communications Limited | 25/04/2017 |
| 01428 589 | Fuse 2 Communications Ltd | 03/07/2017 |
| 01428 598 | Served Up Limited | 01/03/2013 |
| 01428 599 | Served Up Limited | 01/03/2013 |
| 01428 60 | BT | 15/07/1994 |
| 01428 610 | Inclarity Communications Limited | 07/11/2012 |
| 01428 611 | Inclarity Communications Limited | 07/11/2012 |
| 01428 612 | Inclarity Communications Limited | 07/11/2012 |
| 01428 615 | Inclarity Communications Limited | 07/11/2012 |
| 01428 62 | AQL Wholesale Ltd | 01/11/2004 |
| 01428 64 | BT | 15/07/1994 |
| 01428 65 | BT | 15/07/1994 |
| 01428 66 | BT | 15/07/1994 |
| 01428 67 | BT | 15/07/1994 |
| 01428 68 | BT | 15/07/1994 |
| 01428 69 | GCI Network Solutions Ltd | 25/04/2017 |
| 01428 70 | BT | 15/07/1994 |
| 01428 71 | BT | 15/07/1994 |
| 01428 72 | BT | 15/07/1994 |
| 01428 730 | Linear Telecoms Limited | 08/10/2010 |
| 01428 731 | Simwood eSMS Limited | 05/04/2013 |
| 01428 732 | Media Hawk Ltd | 11/04/2013 |
| 01428 734 | IOVOX Limited | 03/07/2012 |
| 01428 735 | Kalnet4U Ltd | 16/05/2013 |
| 01428 736 | I-NET COMMUNICATIONS GROUP PLC | 21/06/2013 |
| 01428 737 | Content Guru Limited | 15/10/2012 |
| 01428 738 | Colt Technology Services | 30/01/2013 |
| 01428 739 | XoverX Ltd | 30/04/2013 |
| 01428 74 | BT | 15/07/1994 |
| 01428 75 | BT | 15/07/1994 |
| 01428 76 | Vodafone Ltd (C&W) | 02/09/2013 |
| 01428 770 | Gamma Telecom Holdings Ltd | 19/11/2012 |
| 01428 771 | Gamma Telecom Holdings Ltd | 19/11/2012 |
| 01428 772 | Gamma Telecom Holdings Ltd | 19/11/2012 |
| 01428 773 | Gamma Telecom Holdings Ltd | 19/11/2012 |
| 01428 774 | Gamma Telecom Holdings Ltd | 19/11/2012 |
| 01428 776 | Gamma Telecom Holdings Ltd | 19/11/2012 |
| 01428 777 | Gamma Telecom Holdings Ltd | 19/11/2012 |
| 01428 778 | Gamma Telecom Holdings Ltd | 19/11/2012 |
| 01428 780 | Magrathea Telecommunications Limited | 17/11/2011 |
| 01428 785 | Magrathea Telecommunications Limited | 17/11/2011 |
| 01428 786 | Magrathea Telecommunications Limited | 17/11/2011 |
| 01428 787 | Magrathea Telecommunications Limited | 17/11/2011 |
| 01428 788 | Magrathea Telecommunications Limited | 17/11/2011 |
| 01428 789 | Magrathea Telecommunications Limited | 17/11/2011 |
| 01428 790 | Six Degrees Technology Group Limited | 14/01/2020 |
| 01428 792 | Six Degrees Technology Group Limited | 14/01/2020 |
| 01428 794 | Six Degrees Technology Group Limited | 14/01/2020 |
| 01428 80 | Invade International Ltd | 20/01/2016 |
| 01428 81 | Vectone Mobile Limited | 30/06/2009 |
| 01428 83 | CFL Communications Ltd | 10/07/2009 |
| 01428 844 | WIGHTFIBRE LIMITED | 28/11/2011 |
| 01428 850 | Digitech Solutions Global Limited | 28/04/2010 |
| 01428 851 | Verizon UK Limited | 05/05/2010 |
| 01428 852 | Calltracks Limited | 20/09/2013 |
| 01428 853 | Affiniti Integrated Solutions Limited | 05/11/2010 |
| 01428 854 | Windsor Telecom Ltd | 21/07/2010 |
| 01428 855 | Atomstream Limited | 23/04/2010 |
| 01428 856 | Telappliant Ltd | 02/06/2010 |
| 01428 857 | Telephone Box Limited | 25/11/2010 |
| 01428 858 | Suretec Systems Ltd | 06/05/2010 |
| 01428 859 | Numbergroup Utilities Ltd | 03/12/2010 |
| 01428 861 | Phone Co-Op Numbering Limited | 22/12/2010 |
| 01428 862 | IP Wholesale Limited | 01/06/2017 |
| 01428 864 | Vodafone Ltd (C&W) | 02/09/2013 |
| 01428 865 | Nexbridge Communications Limited | 07/03/2012 |
| 01428 867 | Numbers Plus Ltd | 28/07/2011 |
| 01428 868 | Orbtalk Limited | 16/09/2011 |
| 01428 870 | Inet Telecoms Ltd (Voipfone) | 05/10/2012 |
| 01428 871 | Inet Telecoms Ltd (Voipfone) | 05/10/2012 |
| 01428 877 | Inet Telecoms Ltd (Voipfone) | 05/10/2012 |
| 01428 879 | Inet Telecoms Ltd (Voipfone) | 05/10/2012 |
| 01428 890 | VOXYONDER NETWORK SERVICES UK LTD | 10/09/2020 |
| 01428 892 | BT | 17/12/2020 |
| 01428 898 | Mi Telecom Limited | 06/07/2020 |
| 01428 900 | Redwood Technologies Ltd | 15/11/2018 |
| 01428 901 | iHub 2 Limited | 18/05/2016 |
| 01428 902 | M247 Ltd | 29/05/2015 |
| 01428 904 | Dial 9 Communications Limited | 10/12/2019 |
| 01428 906 | DIDWW Ireland Limited | 18/01/2019 |
| 01428 907 | IP Voice Networks Ltd | 20/09/2017 |
| 01428 909 | YayYay Limited | 23/04/2015 |