What is VoIP? A Plain-English Explanation for UK Businesses

VoIP stands for Voice over Internet Protocol, and it does exactly what the name says — it carries your voice calls over the internet rather than the old copper phone network. If your business still runs on a traditional landline or ISDN line, you need to understand this now, because the UK's entire public telephone network is being switched off in January 2027.

This guide covers everything you need to know, without the telecoms industry jargon.

The short answer:

• VoIP converts your voice into digital data packets and sends them over the internet — just like an email or a video call
• It replaces traditional landlines and ISDN lines completely
• Calls cost far less: VoIP runs from £5.99 per user per month, compared to £30–£50 per ISDN channel
• You keep your existing phone numbers — geographic, 0800, or otherwise
• Every UK business must switch before 31 January 2027, when the PSTN is shut down for good

How VoIP works (without the jargon)

When you speak into a VoIP phone — or a laptop, mobile, or desk phone connected to VoIP — your voice is converted into small packets of digital data. Those packets travel across your broadband connection to the recipient, where they're reassembled and played back as sound, in real time.

The whole process happens in milliseconds. Done well, the call quality is indistinguishable from a traditional line — often better.

Each active VoIP call uses around 100Kbps of bandwidth. A standard UK fibre broadband connection handles that easily, even with several calls running at the same time.

So for your business: if you have a decent broadband connection and a router, you already have the infrastructure VoIP needs. The heavy lifting happens in the cloud, not on your premises.

What VoIP replaces — and why that matters

For decades, UK businesses have relied on the Public Switched Telephone Network (PSTN) — the copper wire network that BT originally built and that still carries most landline calls today. ISDN (Integrated Services Digital Network) is the business-grade version of that same infrastructure.

Openreach announced the full switch-off of both PSTN and ISDN for 31 January 2027. That date applies to every business in the UK, regardless of size, sector, or location. After that point, traditional landlines stop working entirely.

31% of UK businesses have already migrated to VoIP. The remaining 69% need to act — and the businesses that leave it until 2026 will face a scramble for engineers, numbers, and support.

The good news: switching to VoIP is not the major upheaval it sounds like. Most businesses go live within 10 working days, keep all their existing phone numbers, and immediately pay less per month than they did before.

Your current phone system is being retired whether you plan for it or not. Getting ahead of that now, on your own timeline, is the sensible move.

VoIP vs traditional landline: what actually changes

The biggest change is where your calls travel. Traditional landlines use dedicated copper circuits — you pay for that circuit whether anyone picks up the phone or not. VoIP uses your existing broadband, and you pay per user, not per line.

Here is what that means in practice:

Cost. ISDN lines typically run £30–£50 per channel per month. VoIP starts at £5.99 per user per month. For a team of five, that difference adds up to thousands of pounds a year.

Flexibility. With a traditional line, your number is tied to a physical location. With VoIP, your number travels with you. Your team can take calls on their laptops, mobiles, or desk phones from anywhere with an internet connection. That matters if you work across multiple sites, have remote staff, or simply want business calls to route to your mobile when you're out.

Features. Auto-attendants, call recording, hunt groups, voicemail to email, call analytics — these are built into most VoIP plans. On a traditional ISDN system, each of those features either doesn't exist or costs extra to bolt on.

Scalability. Adding a new line on ISDN means contacting your provider, waiting for an engineer, and paying an installation fee. Adding a VoIP user takes minutes and costs nothing extra to set up.

What stays the same: your phone numbers, the way your team makes and receives calls, and the experience for the person on the other end of the line.

What your business needs to run VoIP

The requirements are simpler than most people expect.

Broadband connection. You need a reliable broadband connection — fibre is ideal, but a good ADSL connection works fine for smaller teams. Remember, each simultaneous call uses around 100Kbps. A 10Mbps connection comfortably handles 50 concurrent calls.

A router. Your standard business router is almost certainly sufficient. The only thing worth checking is that it doesn't apply heavy traffic shaping that deprioritises voice data.

Phones or devices. You have three options. IP desk phones plug directly into your network and work exactly like a traditional phone. Softphones are apps installed on a laptop or computer — free to set up, and useful for hybrid teams. Mobile apps let staff take business calls on their smartphones, with the business number showing as the caller ID. You can mix all three across the same account.

A VoIP provider. This is where it pays to choose carefully. You want a direct provider — one that controls its own infrastructure — not a reseller who depends on another company's platform and support team.

That is the only list. No on-site hardware, no engineers, no server room.

How VoIPninjas compares

VoIPninjas is a direct UK VoIP provider based in Christchurch, Dorset. Direct means we own and operate our own network — we are not reselling someone else's platform. When something needs fixing, we fix it. When you call support, you speak to someone who actually knows the system.

There are three plans, all on a 28-day rolling agreement with no setup fees:

Ronin — £5.99/user/month 100 inclusive UK minutes. Right for light users: a reception line, a secondary number, or a team member who mostly receives calls.

Samurai — £14.99/user/month 750 inclusive UK minutes. The most popular choice for small and medium businesses with moderate outbound call volumes.

Shogun — £24.99/user/month Unlimited UK calls plus calls to 55 countries. Built for businesses that call frequently, handle customer service at volume, or have international contacts.

All plans include number porting (bring your existing numbers across), voicemail to email, and access to the full feature set. No contracts. No hidden activation charges.

You can trial the service for 14 days, free of charge, with no card required. Most businesses are fully live within 10 working days of signing up.

Ready to see what VoIP costs your business? Get your numbers ported, your team set up, and your calls running — in under two weeks, with no long-term commitment. Start your free 14-day trial → Or call us on 0330 043 2388 — we'll talk it through with you. No tie-in, no setup fees. Most businesses are fully live within 10 working days.

Frequently asked questions

Will my phone number change if I switch to VoIP?

No. Number porting lets you bring your existing geographic number, 0800 number, or any other business number across to VoIP. Your customers dial the same number they always have. The only difference is that calls now travel over the internet instead of copper. VoIPninjas handles the porting process for you — it typically takes 7–10 working days.

Is VoIP reliable enough for a business that depends on its phones?

Yes, provided your broadband connection is stable. VoIP call quality over a modern fibre connection is equal to or better than a traditional landline. The main variable is your internet connection — if your broadband is solid, your calls will be solid. VoIPninjas monitors call quality across its network and routes traffic to maintain performance. For businesses that want an extra layer of resilience, calls can automatically failover to mobile if the broadband drops.

Can my team use VoIP while working remotely?

That is one of the strongest arguments for switching. Every user on a VoIP system can make and receive calls from anywhere with an internet connection — using a desk phone, laptop app, or mobile app — with the business number showing as their caller ID. For businesses with remote or hybrid teams, this removes the need for call forwarding workarounds and keeps all calls within the same system, with the same reporting and management tools.

How long does it take to switch to VoIP?

Most businesses are fully live within 10 working days. The process involves porting your existing numbers, configuring your call routing, and setting up devices for each user. VoIPninjas manages the technical side. You do not need an IT team or any specialist knowledge. The 14-day free trial lets you test the system in parallel with your existing phones before you commit to switching over entirely.