SIP Trunking / ISDN Services Business Phone Services

Products & Services

Colt has an unquestionable leading position in the SIP Trunk solution market, offering a feature-rich product fully tested and certified for all main IP PBX vendors. Learn more about our business phone services below.


SIP Trunking

With our SIP Trunk solution 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%.

ISDN Voice

ISDN services

With over 20 years’ experience, and the most comprehensive Pan-European network, Colt is the ISDN Services provider of choice for thousands of businesses across Europe.

The telecom industry has been transitioning business phone services from legacy ISDN to the next generation voice over IP technology – SIP trunking. Having launched SIP trunking over a decade ago, Colt has an unquestionable leading position in this market, offering a feature-rich product fully tested and certified for all main IP PBX vendors. As Colt now delivers its ISDN services over SIP trunking as well, it provides a seamless migration path for customers to go from ISDN to SIP trunking, that allows them to move to voice over IP at their own preferred pace. Colt ISDN over SIP offers all the features but with increased flexibility to distribute inbound traffic.

See how businesses are using Colt's business phone services
Business phone services case studies →

Colt's business phone services are available on a global network
Learn about the Colt IQ Network →

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

Cloud Telephony and Unified Communications Solutions
Colt Cloud UC is a flexible and scalable, fully managed, cloud-based one stop shop solution that comprises of IP Telephony and Unified Communications, provided to customers as a service.

Toll Free & International Business Phone Numbers
Colt Intelligent Network (IN) Services is a managed portfolio of inbound voice services that provide our customer’s callers with an improved user experience, whilst maximising the performance of the customer’s call centre.

Service Provider Solutions
A portfolio of comprehensive Wholesale VoIP propositions addressing the needs of Carriers, Resellers and Service Providers.

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