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8 Jan, 2026
ISDN Replacement Solutions in the UK for Telecommunications
Future-proof your telecoms communications with a seamless ISDN-to-SIP migration.
Migrate Before the Deadline
Openreach is switching off ISDN across the UK. We ensure your business is migrated well ahead of the deadline with zero disruption.
Better Features
Modern VoIP alternatives offer features ISDN never could — video calling, mobile integration, and flexible call routing.
Lower Costs
Most businesses see significant monthly savings after migrating from ISDN to VoIP, often reducing telephony costs by 40% or more.
Telecoms still relying on ISDN lines face an urgent deadline: the UK PSTN network is being switched off, and every ISDN line will cease to function. For telecoms using ISDN for voice calls, network telemetry, customer provisioning data, and CDRs transfers, or alarm systems, failing to migrate in time means network management platforms losing visibility during outages and complete loss of telephone service.
Cloudswitched provides modern ISDN replacement solutions for UK telecoms, migrates your business from legacy ISDN lines to modern SIP trunks and VoIP, ahead of the 2025 PSTN switch-off, with improved call quality and lower costs. We audit your existing ISDN usage, design a modern SIP-based replacement, and manage the entire migration so your network engineers and support staff experience no disruption to their communications.
How it works for Telecoms businesses
A clear, structured process from consultation to ongoing support.
1
Comprehensive Audit
We audit every ISDN line, channel, and number in your business — including those used for alarms, lifts, fax machines, and card payment terminals — to ensure nothing is missed.
2
Tailored Replacement Plan
Based on your audit, we recommend the right combination of VoIP, SoGEA, and analogue adapters to replace every ISDN service with a modern equivalent.
3
Managed Migration
We port your numbers, configure new systems, and test everything before decommissioning your old ISDN lines. Your team experiences zero downtime during the switch.
ISDN Replacement Solutions in the UK for Telecoms
Seamless Migration
We port your existing telephone numbers and replicate your current call routing, so your network engineers and support staff and clients experience zero disruption when ISDN lines are replaced with SIP trunks.
Significant Cost Savings
SIP trunks typically cost 40-60% less than equivalent ISDN lines. For telecoms with multiple lines across offices, exchanges, and data centres, the savings are substantial and immediate.
Enhanced Call Quality
Modern SIP trunks deliver HD voice quality that surpasses ISDN, ensuring your network engineers and support staff present professionally on every call with clients, suppliers, and telecoms contacts.
Future-Proof Technology
Unlike ISDN, SIP trunks integrate with modern telecoms platforms and support features like video calling, call recording, and CRM integration with OSS/BSS platforms, network monitoring, and provisioning tools.
ISDN Replacement Service Includes
Full audit of existing ISDN lines and services
Replacement technology recommendation and planning
Number porting to preserve all existing phone numbers
Alarm, lift, and fax line migration solutions
Zero-downtime cutover with pre-migration testing
Post-migration support and optimisation
Why Telecoms businesses choose us
Hundreds of successful ISDN migrations for telecoms across the UK
Understanding of telecoms telephony requirements and call patterns
Number porting with zero downtime and no lost calls during migration
Integration expertise with OSS/BSS platforms, network monitoring, and provisioning tools for click-to-call and call logging
Free ISDN audit identifying all lines, usage patterns, and migration priorities
UK-based support team available throughout the migration and beyond
Frequently Asked Questions
The UK PSTN switch-off means all ISDN lines will stop working. Openreach has already stopped selling new ISDN lines and is actively migrating exchanges. Telecoms should begin their migration now to avoid service disruption and secure the best SIP pricing.
No. Cloudswitched ports all your existing telephone numbers to SIP trunks, so your network engineers and support staff, clients, and all published contact details remain unchanged throughout the migration.
Most telecoms save 40-60% on line rental and call charges by migrating from ISDN to SIP trunks. A typical offices with 8 ISDN channels saves approximately £200 per month, adding up to over £2,400 annually.
We audit all ISDN-dependent equipment including alarm panels, fax machines, and EPOS terminals. Each device is migrated to a suitable IP-based alternative, ensuring no telecoms system loses functionality during the transition.
A typical ISDN migration for telecoms takes 2 to 6 weeks from audit to completion. Cloudswitched manages the entire process, including number porting, SIP configuration, and handset setup, with a dedicated project manager for your telecoms migration.
Free On Boarding worth up to £2,000!
Limited time offer - valid until 31/05/2026
Start Your ISDN Migration Today
Get ahead of the switch-off. Share your details and we will conduct a free audit of your ISDN estate.
Submit your details and one of our friendly team members will be in touch shortly