The phone line that quietly powered your alarms, lift lines, card machines and desk phones for years is being retired. For many businesses, the real challenge is not understanding that the PSTN switch-off is happening – it is working out how to migrate from PSTN without causing problems for staff, customers or day-to-day operations.
If you are responsible for business continuity, this is less about buying a new phone system and more about making sure every service that depends on your existing lines is identified, replaced and tested properly. Done well, the move is straightforward. Left too late, it can become a rushed project with avoidable gaps in service.
What migrating from PSTN actually involves
When people ask how to migrate from PSTN, they often think first about replacing handsets. In reality, the process usually reaches further than voice calls. Traditional PSTN and ISDN lines may also support broadband, payment terminals, fax machines, door entry systems, franking machines, security alarms or emergency lines.
That is why the first step is not choosing technology. It is understanding what your current setup is doing today.
For some organisations, the migration will be relatively simple. A small office using a few analogue lines may only need a reliable business broadband connection and a hosted VoIP phone system. For a larger site or multi-location business, there may be more moving parts, including number porting, network upgrades, handset rollout, integration with Microsoft Teams, and planning for services that cannot tolerate downtime.
Start with an audit, not assumptions
A proper audit gives you the foundation for every decision that follows. You need a clear view of all active lines, associated numbers, contract end dates, broadband dependencies and any non-voice services running over the network.
This is where many businesses uncover surprises. A line installed years ago for a fax machine may now support a lift emergency phone. A backup line may still be tied to a payment terminal. An old number that nobody talks about may still receive calls from longstanding customers.
It helps to document three things. First, what each line or service is used for. Second, how critical it is to operations. Third, what the replacement option should be. That approach keeps the project practical and reduces the risk of missing something important.
Choose the right replacement for the way you work
There is no single answer to how to migrate from PSTN because the right solution depends on your business setup, connectivity, and how your teams communicate.
For most businesses, internet-based telephony is the natural replacement. A cloud VoIP system can support desk phones, mobile apps, call routing, voicemail, reporting and remote working without the limitations of older line-based systems. It also tends to make future changes easier, whether you are adding users, opening another site or enabling hybrid working.
That said, not every migration is identical. Some organisations want a full hosted phone system. Others prefer a Microsoft Teams telephony setup because staff already work in that environment. Some need contact centre features for customer-facing teams. Others simply need dependable voice calling and number retention.
The important point is fit. The best replacement is the one that supports your operational needs today without creating unnecessary complexity tomorrow.
Check your connectivity before moving voice services
Voice over IP depends on a stable data connection. If your broadband is unreliable, underpowered or shared across a busy network without proper configuration, call quality will suffer.
Before migrating, review your connectivity in practical terms. Consider current bandwidth, resilience, router capability, internal network performance and whether voice traffic should be prioritised. A small business with light call volumes may be well served by a straightforward business broadband service. A larger organisation with heavy voice usage, multiple sites or critical uptime requirements may need a more resilient setup with failover options.
This is often where a little planning prevents a lot of frustration. Businesses sometimes focus heavily on the new phone platform while overlooking the connection underneath it. If the foundation is weak, the experience will be too.
Plan number porting carefully
For most businesses, keeping existing numbers matters. Customers know them, marketing materials include them, and changing them can create confusion you simply do not need.
Number porting is usually very manageable, but it needs coordination. You will want to confirm exactly which numbers are being retained, who currently controls them, and whether any services are bundled together in a way that could affect the transfer.
Timing matters here. Port a number too early without the right preparation and you risk disruption. Leave the paperwork too late and the wider migration may stall. A well-managed migration plan builds number porting into the project rather than treating it as an afterthought.
Do not forget lines that are not used for calls
One of the biggest PSTN migration risks is assuming every line is there for telephony. In reality, many analogue services sit quietly in the background until the day they stop working.
Alarm systems, EPOS terminals, careline devices, entry systems and lift emergency phones all need special attention. Some can move to IP-based services. Some may need mobile-based alternatives. Others require supplier-specific upgrades.
This is the part of the project where expert guidance is especially valuable, because each service may involve a different provider, timescale or technical requirement. A calm, methodical review avoids the common problem of replacing the phone system while leaving hidden dependencies unresolved.
Roll out in stages where it makes sense
Not every business should switch everything at once. A phased migration can reduce risk, especially for organisations with multiple departments, sites or specialist services.
For example, you might upgrade connectivity first, move core telephony second, and handle alarms or door entry systems as separate workstreams. Or you may start with a pilot group to test call flows, devices and user experience before a wider rollout.
There is a trade-off. A single cutover can be quicker and simpler to manage on paper, but it puts more pressure on one go-live date. A phased approach gives you more control, though it can require tighter coordination over a longer period. The right route depends on your business tolerance for change and the complexity of your estate.
Prepare your people as well as your systems
Even when the technology is right, migrations can feel disruptive if staff do not know what is changing. A new handset, softphone app or Teams calling setup is not difficult to learn, but people still need clear communication and a bit of support.
Keep training practical. Show staff how to make and transfer calls, access voicemail, use presence settings and handle calls when working remotely. If reception or customer service teams use more advanced features, give them extra guidance in advance.
Good communication helps here. Let people know what is changing, when it is happening and who to contact if something does not look right. A friendly support process makes the transition feel controlled rather than stressful.
Test before, during and after go-live
Testing is what turns a migration plan into a dependable live service. Before go-live, confirm call quality, inbound and outbound routing, voicemail, hunt groups, auto attendants and any integrations. Test number presentation and failover arrangements too.
On the day of migration, verify the essentials first. Can customers reach the right teams? Can staff place calls reliably? Are critical business functions working as expected?
After go-live, keep monitoring. Some issues only appear under normal usage, especially across busy periods or mixed office and remote working environments. A short period of close support after launch often makes all the difference.
Common mistakes to avoid when you migrate from PSTN
Most PSTN migration problems are not caused by the switch itself. They come from weak planning. Businesses get caught out when they underestimate line dependencies, delay decisions on connectivity, or assume porting will happen instantly.
Another common issue is choosing a replacement based only on headline features rather than operational fit. A system can look impressive but still be wrong for your call handling, reporting needs or user habits.
It is also worth avoiding the temptation to leave everything until the final months. Supplier availability, internal approvals and third-party dependencies can all affect timescales. Starting earlier gives you more options and a calmer process.
The value of a managed migration
A managed migration takes pressure off internal teams by giving you a clear plan, technical oversight and one point of coordination. That is especially useful if your current setup has grown organically over the years and nobody has a complete picture of it.
With the right partner, the process becomes simpler. You can audit existing services, agree the best-fit replacement, prepare the network, manage number porting, schedule rollout and support users without turning the project into a drain on daily operations. For many organisations, that combination of technical expertise and practical support is what keeps the migration on track.
If you are still working out how to migrate from PSTN, the best next step is not to rush into replacement decisions. Start by understanding what you have, what your business actually needs, and what a well-planned transition should look like. Once that is clear, the move becomes far more manageable – and a good deal less disruptive than many businesses expect.
