Moving from ISDN to VoIP.
BT switches off ISDN and copper PSTN by January 2027. Every UK business on copper has to migrate. Telexico handles the move end-to-end — number porting, parallel running, scheduled cutover, zero business disruption.
What we hear every week.
The frustrations behind why businesses search for moving from isdn to voip in the first place. If any of these feel familiar, the fix is straightforward.
ISDN switch-off deadline is 2027 — and it's real
BT switches off ISDN and copper PSTN by January 2027. After that, no ISDN. Every UK business still on copper has to migrate.
Worry about losing the phone number
Existing business numbers carry years of marketing, customer history, Google listing equity. Number porting concerns stop businesses moving — we handle it cleanly.
Worry about downtime during cutover
Mid-day phone outages aren't acceptable. We schedule cutovers out-of-hours with parallel running so old and new services coexist during the migration.
Multiple ISDN lines with complex routing
Businesses on multi-line ISDN with DDIs, hunt groups, after-hours diversion — the existing routing logic needs replicating on hosted VoIP. Done wrong, calls get lost in the migration.
ISDN to VoIP migration, managed end-to-end
Telexico handles ISDN-to-VoIP migration as a project, not a single transaction. **Week 1 — Discovery:** existing ISDN setup documented (lines, DDIs, hunt groups, voicemail rules, diversion logic, hardware). **Week 2-3 — Design and quote:** hosted VoIP tenant designed to replicate (or improve) existing routing; new IP handsets specified; integration with broadband, AI receptionist, mobile apps planned. **Week 4-5 — Order placement:** Number porting initiated (BT typically 2-4 weeks), new VoIP tenant configured, IP handsets shipped. **Week 5-6 — Parallel running:** New hosted VoIP live on temporary numbers, staff training, old ISDN still active. **Week 6-7 — Cutover:** Out-of-hours number port, old ISDN ceased, new system takes over. **Week 7-8 — Post-cutover monitoring:** Engineer on standby, any teething issues resolved quickly. Old ISDN line ceased after successful cutover.
The Telexico approach to moving from isdn to voip.
Six things our customers consistently tell us matter.
Project-managed migration
One Telexico project manager owns the migration from discovery to post-cutover — clear status updates throughout.
Number porting handled cleanly
All your existing UK numbers transfer to hosted VoIP — no stationery, website or Google listing changes needed.
Parallel running for 1-2 weeks
Old ISDN and new VoIP coexist during the migration — staff trained, customers unaffected, switchover scheduled.
Out-of-hours cutover
Switch happens at a time that suits your operation — typically evenings or weekends to minimise customer-visible interruption.
Routing logic replicated or improved
Hunt groups, DDIs, voicemail rules, after-hours diversion — replicated on hosted VoIP, often improved with modern features like AI receptionist.
One provider afterwards
Bundle the new hosted VoIP with broadband, WiFi and AI receptionist — single Telexico relationship, single bill, single support.
Built around real UK business migration risk
Most UK businesses can't afford a day of phone downtime to migrate. Our approach is designed around that reality — parallel running, scheduled out-of-hours cutover, post-migration monitoring. The business carries on operating; the migration happens around it. We've migrated hundreds of UK businesses from ISDN to hosted VoIP without operational disruption — including multi-line setups with complex routing.
How it works for businesses like yours.
Three real-world setups we deliver across the UK.
SMEs on single or dual ISDN lines
Standard small business migration — typically 4-6 weeks elapsed, parallel running, scheduled cutover. Done routinely.
Multi-line ISDN with DDI ranges
Larger businesses with multi-line ISDN30, DDI ranges, complex hunt groups — migration takes longer (6-10 weeks) but routing replicated faithfully.
Healthcare and regulated practices
GP practices, dental, professional firms with compliance requirements — call recording continuity, audit trails, GDPR-compliant data handling all maintained.
Why UK businesses choose Telexico for ISDN to VoIP migration
We've migrated hundreds of UK businesses from ISDN to hosted VoIP — converted offices, retail, hospitality, healthcare, manufacturing, multi-site. Project-managed, parallel-run, scheduled cutover, post-migration monitoring. UK engineers, UK support, one provider relationship afterwards.
What you actually get from Telexico.
Honest about scope. No aggressive sales tactics, no surprise renewal jumps, no tier-1 call-centre triage. Real UK engineers, transparent pricing, one provider relationship across the stack.
UK-based provider
Wolverhampton-headquartered. Engineers cover the West Midlands daily; UK-wide install via our partner network. Real UK engineer support, UK data residency, UK contractual relationship — not US-routed SaaS.
Real engineer support
When you call Telexico, you reach someone who can actually fix things. Response SLA backed by real engineering capacity rather than call-centre headcount. Named account manager for ongoing customers.
Free infrastructure review
Every engagement starts with a no-obligation audit of your current setup. Honest recommendation — sometimes that's "stay with your current provider after negotiation." We'd rather be honest than oversell.
Transparent pricing
What you sign for is what you pay — including renewal. No teaser pricing that jumps 30-100% at year two. No mid-contract CPI shock. Predictable multi-year cost from day one.
One provider, one platform
Broadband, hosted VoIP, business WiFi, AI Receptionist, 4G/5G failover, CCTV consolidated onto one Telexico relationship. Single bill, single support number, single engineer when something needs attention.
Migration project-managed
Switching to Telexico isn't DIY. We handle contract audit, notice timing, ordering, parallel running, cutover, old-provider close-out. Customer-visible disruption typically measured in minutes.
Tailored around your business.
Tell us what you have now and what's frustrating you. We'll come back with a tailored review of where we can simplify, consolidate or improve it — no fixed-package pressure, no hard sell.
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Free infrastructure review
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Frequently asked questions
When does ISDN actually get switched off?
BT is currently rolling out the PSTN switch-off — different exchanges at different times — with the full switch-off deadline of January 2027. Many UK exchanges are switching off ISDN earlier than that. Don't assume you have until the deadline; check your specific exchange's date.
Do I really have to migrate from ISDN?
Yes — there's no extension. After your exchange switches off PSTN/ISDN, your existing phone service stops working. The only options are hosted VoIP or, in very specific cases, SoGEA + alternative service. Most UK businesses are migrating to hosted VoIP.
How long does ISDN to VoIP migration take end-to-end?
Typically 4-8 weeks elapsed from kick-off to live. Number porting is the long-lead item (2-4 weeks). Active project work concentrated at the start (discovery/design) and the cutover window (a few hours). Complex multi-line setups can be 8-12 weeks.
Will I lose my phone numbers?
No — number porting moves them across cleanly. All your existing UK landline numbers transfer to hosted VoIP without changing your stationery, marketing, Google listing, or what customers dial. Porting is standard and routine.
How much downtime is there?
Typically a few minutes — sometimes seconds — during the actual cutover. Often customer-invisible. Scheduled out-of-hours. Old ISDN line stays live until the cutover so the business runs on the existing service right up to the moment of switch.
What about my existing phone hardware?
Most ISDN handsets don't work with hosted VoIP — different protocol. Telexico supplies new IP phones (Yealink typically) as part of the install. Existing IP phones from previous VoIP setups can sometimes be re-used. Old ISDN handsets disposed of cleanly.
How much does ISDN to VoIP migration cost?
Indicative: project fee for the migration work (typically £200-1,500 depending on complexity); new IP phones £80-200 each; ongoing hosted VoIP £8-15 per user per month; ongoing broadband £40-100/month. Often the new monthly cost is lower than the old ISDN bill, so the project pays for itself within months.
Apply this to your business?
Reading the guide is one thing; applying it to your specific operation is another. Send us your current setup — we'll review what you have, what fits, and where to start. No hard sell, no fixed-package pressure.