Log in to Colt Online Accessibility English SIP Trunking / ISDN Services Business Phone Services Products & Services Home ❯ SIP Trunking / ISDN Services Business Phone 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 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. Live chat with Sales For all your purchase enquiries. Monday to Friday 9am - 5pm Chat with us Contact us Company Size 0-500 501-2000 2001-5000 5001-10,000 10,000+ Are you a Colt customer?* Yes No Solution(s) of interest* Cloud connectivity Voice Services Capital Markets Cybersecurity Internet access Other By submitting this form you have read and agreed to our Data privacy statement. Looking for customer support? Visit our support hub. Call a specialist +44 (0) 20 7863 5510 Monday to Friday 9am - 5pm Contact Us Support Complaints Careers Legal Covid-19 Terms & Conditions Code of Business Conduct Data Privacy Information © 2021 Colt Technology Services Group Limited Colt Online Colt Interactive This website uses cookies to make our site work, for marketing purposes and to improve your online experience. We won‘t set optional cookies unless you enable them. You can change your cookie settings at any time. Further information can be found in our Privacy Policy and Terms of Use. See more information here Accept all cookies Cookies settings