ISDN Voice Services

Consolidate and simplify your voice services while reducing costs. A single network and supplier means one, reduced, flat fee, with extra savings to be made by centralising the telephony network through consolidation of Local Area Codes.

Using the ISDN Service in combination with Colt Business Internet Access can further decrease your costs and once you are fully IP ready, you can easily migrate to a SIP Trunking Service, which is even more cost effective.

Pan-European reach with reliability guaranteed

Our robust network is protected by Dual Homing, Disaster Recovery or Inbound Call Re-routing services, ensuring your business stays up and running should the unexpected happen. Because we fully own and operate our own network across 50 geographically diverse, carrier grade switches and SIP Trunking POPs, we can guarantee a seamless experience across 13 countries in Europe, compliant with all legal and regulatory requirements.

Flexible and transparent

Online call detail records (CDR) give you complete visibility of call spend and traffic, while All Inclusive or Bundled Minutes with Flat Fees or Pay-As-You-Go tariffs suit customers of all sizes and traffic levels.

Our own number pool across Europe as well as extensive porting capabilities allows you to keep your current numbers, or add new ranges, with no disruption to the business.

Future proof

Next Generation IP Technology can help customers transition from legacy telephony to new voice technologies, such as SIP Trunking and Unified Communications, enabling them to stay competitive and agile. With over 20 years’ experience, and the most comprehensive Pan-European network, Colt is the ISDN provider of choice for thousands of businesses across Europe.

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Emergency Calls in Japan

Want to learn more about our business phone services?
Check out the rest of the products below.

SIP Trunking Services
With SIP Trunking you simplify all your telecommunications into a single IP network. You keep all the features of traditional telephony, and call quality, while gaining a monthly cost saving as high as 50%.