Every UK business with a phone system is facing the same deadline. BT's PSTN switch-off in January 2027 will retire the traditional analogue and ISDN network that the majority of on-premise phone systems depend on. For businesses that have not yet migrated to a cloud-based alternative, the clock is running.
The question is not whether to move. It is which platform to move to, and how to do it without disrupting operations in the process.
For businesses on legacy PBX or ISDN, Zoom Phone is one of the most straightforward migration paths available - not because of marketing, but because it solves the PSTN replacement problem cleanly for a specific type of organisation. This guide covers what Zoom Phone is as a business phone system, who it suits, what to check before committing, and how to run the migration without the common pitfalls.
If you are evaluating cloud telephony options ahead of the PSTN deadline, this is the practical starting point.
TL;DR: The PSTN switch-off in January 2027 means every UK business on legacy telephony must migrate. Zoom Phone is a clean option for businesses replacing on-premise PBX - it consolidates voice, video, and messaging on one platform with no hardware required. The migration window is tighter than it looks: number porting alone takes 4-6 weeks. Start the assessment now.
Zoom Phone is a cloud-based business phone system, a direct replacement for traditional PBX or on-premise telephony, delivered entirely over the internet. It handles inbound and outbound calls, call routing, auto-attendant, hunt groups, voicemail with transcription, and call recording - everything a business phone system needs to do, without the physical hardware.
What separates it from a standalone VoIP system is where it sits architecturally. Zoom Phone is built into the same platform as Zoom Meetings and Zoom Team Chat. That means calls, video, and messaging run from a single app, a single admin portal, and a single licence structure. A call can be escalated to a video meeting in one click. Voicemails sit alongside team messages. Call recordings are stored and searchable in the same place as meeting recordings.
Core capabilities included as standard for UK businesses:
For businesses replacing a legacy PBX, the practical benefit is a clean cutover onto a single cloud platform — no hardware refresh, no ISDN dependency, no separate telephony contract to manage alongside everything else.
The migration value is consolidation, not just capability. Fewer platforms means fewer admin portals, fewer vendor contracts, fewer integration headaches, and a single support relationship when something goes wrong.
BT's PSTN switch-off is the single biggest forcing function for UK business telephony in a generation. From January 2027, the public switched telephone network - the infrastructure that underpins traditional analogue and ISDN phone lines - will be retired. Any phone system that depends on those lines will stop working.
The businesses most at risk are those running:
Many businesses assume their system is already cloud-ready because they moved to hosted VoIP several years ago. That is not always true. Some hosted systems still rely on ISDN backhaul. Checking the connectivity layer - not just the platform - is the first step.
The January 2027 deadline sounds distant. It is not, for three reasons.
Number porting takes time. Porting existing UK numbers to a new platform typically takes 4-6 weeks for straightforward scenarios, longer for complex multi-site or DDI-heavy migrations. Businesses that start late will be porting under pressure.
Implementation resource will be constrained. Every UK business on legacy telephony is facing the same deadline. The pool of implementation partners with capacity to manage complex migrations will tighten through 2026. Businesses starting now have access to resource that will not be available in Q4 2026.
Staff adoption takes time. A phone system migration is not just a technical project. It is a change management exercise. Giving staff time to learn a new system before it becomes the only system reduces risk and improves adoption rates.
|
Stage |
Typical Duration |
|---|---|
|
Requirements assessment and platform selection |
2-4 weeks |
|
Procurement and provisioning |
1-2 weeks |
|
Number porting |
4-6 weeks |
|
Configuration and testing |
2-3 weeks |
|
Staff training and go-live |
1-2 weeks |
|
Total |
10-17 weeks |
Starting in Q3 2026 is cutting it fine. Starting now is the right call.
Zoom Phone is not the right answer for every business. The honest assessment depends on four factors.
The migration path to Zoom Phone is cleanest for businesses moving directly from on-premise PBX or ISDN. If your current system is already cloud-based but underperforming, the transition is still straightforward but requires more careful data migration planning. If your organisation runs primarily on Microsoft 365 and Teams, Microsoft Teams Phone is worth evaluating alongside Zoom Phone before committing.
Zoom Phone handles business telephony cleanly. For businesses with a contact centre requirement - omnichannel routing, queue management, AI virtual agents, quality management, workforce management - Zoom Phone alone is not the answer. The right solution is Zoom Contact Centre, which extends the Zoom Phone foundation with full CCaaS capability. If contact centre is a significant part of your requirement, scope both together from the outset.
Businesses with a large DDI (Direct Dial In) estate, multiple sites, or complex routing requirements need to factor porting complexity into the platform decision. Zoom Phone handles complex porting well, but it requires lead time and planning. A single-site business with 20 numbers is a very different migration to a multi-site business with 500 DDIs and site-specific routing rules.
Zoom Phone's native CRM integrations cover the major platforms. Businesses with bespoke or legacy CRM systems should verify integration options before committing. Custom integrations are possible via the Zoom Phone API, but they add implementation cost and complexity.
Zoom Phone is likely the right fit if:
Consider alternatives if:
The businesses that migrate to Zoom Phone without disruption share one characteristic: they do the groundwork before they start the technical work. Here is what that looks like in practice.
Before any migration begins, document what you have. How many numbers, across how many sites? What call routing rules are in place and why? What integrations does your current phone system have with CRM or other business systems? What analogue lines are connected to non-phone devices like fax machines, door entry, or fire alarms?
This audit is not glamorous, but it prevents the most common migration surprises. Undocumented routing rules and forgotten analogue device connections are the two most frequent causes of migration delays.
Number porting should be initiated as early as possible in the migration process. The porting timeline is largely outside your control once it is submitted - carriers set the pace. Submit porting requests as soon as the platform decision is confirmed, not after configuration is complete.
For businesses with geographic numbers across multiple sites, plan the porting sequence carefully. Porting all numbers simultaneously carries more risk than a phased approach by site or department.
For businesses where telephony is business-critical, running the old and new systems in parallel during the cutover period reduces risk significantly. Staff can be trained on the new system before the old one is switched off, and any configuration issues can be resolved without affecting live calls.
A phone system migration that is technically perfect but poorly adopted is a failed migration. Staff need to understand not just how to use the new system, but why it is better for them - the mobile app, the voicemail transcription, the ability to take calls from any device. Adoption drives the ROI; the technology alone does not.
Fortay Connect is a certified Zoom partner specialising in cloud telephony migrations for UK businesses. We assess your current system, manage the porting process, handle configuration, and ensure your team is set up to get full value from day one. With the PSTN switch-off approaching, contact us to discuss your migration requirements and we will help you move at the right pace, without the risk.