The complete guide to business phone systems.
Everything a UK business needs to know about modern phone systems — how they work, what they cost, and how to choose the right one.
What is a business phone system?
A business phone system is the platform that handles all of your organisation’s calls — routing them to the right people, holding callers in queues, offering menu options, recording conversations and connecting your team whether they’re at a desk, at home or on the move. Modern systems do far more than the old switchboard: they tie together calls, voicemail, mobile apps and reporting into one managed service.
For most UK businesses today, that means a cloud-based system. Instead of a physical box in a comms room, the “brain” of the phone system lives in secure data centres, and calls travel over your internet connection. This is what people mean by hosted VoIP or a cloud PBX, and it’s rapidly replacing the traditional on-premise systems that depended on ISDN and analogue lines.
Why traditional systems are being retired
The UK’s old public switched telephone network (PSTN) and ISDN lines are being switched off by the end of January 2027. After that, the analogue and ISDN lines that many older phone systems rely on will stop working. Every business still using them will need to move to an internet-based system before then.
This isn’t just a compliance deadline — it’s an opportunity. Moving to a cloud phone system almost always lowers monthly costs, adds flexibility and unlocks features that simply weren’t possible on the old network.
Types of business phone system
Hosted VoIP / Cloud PBX: the modern standard — fully hosted, no on-site hardware, calls over the internet, pay per user. Ideal for the vast majority of businesses.
On-premise PBX: a physical system you own and maintain on-site. Increasingly rare due to cost, maintenance and the switch-off.
Microsoft Teams Phone: calling added directly into Teams via Direct Routing — excellent if your team already lives in Teams all day.
SIP trunks: a way to keep an existing capable PBX but replace the old ISDN lines feeding it with internet-based connections.
Key features to look for
Call routing and hunt groups so calls always reach someone; IVR auto-attendant menus (“press 1 for sales”); voicemail-to-email; mobile and desktop apps so staff can work anywhere; call recording for quality and compliance; and reporting so you can see call volumes, missed calls and team performance.
For busier operations, look for queues with announcements, wallboards, CRM integration and call analytics. A good provider will configure these around how you actually work, not hand you a generic template.
How much does a business phone system cost?
Cloud phone systems are typically priced per user per month, often from around £5 per user, with no large upfront cost. You pay for the number of people who need an extension, and you can scale up or down as your team changes.
Compared with a traditional system — hardware, installation, line rental and maintenance — cloud usually works out significantly cheaper over its life, while adding features and flexibility the old kit never had.
How to choose the right system
Start with how your team works: office-based, hybrid, fully remote or multi-site. Then think about call volumes, whether you need queues and menus, and any compliance requirements such as call recording. Finally, consider whether you want a classic handset-based system or calling built into Teams.
The most important choice is the provider. A local, independent provider that sets the system up properly and supports it directly will save you far more than a fractionally cheaper price from a faceless national reseller.
Migrating without disruption
A good migration keeps your existing numbers (we port them across), runs the new system alongside the old where needed, and cuts over with minimal downtime — often measured in minutes. New numbers can be live within the hour; porting an existing number takes a little longer and is scheduled carefully.
The key is planning: a provider who audits your current setup, times the move and supports you through it makes switching genuinely painless.
What does your team actually need? The honest sizing guide
Phone systems are sold by feature count; they should be bought by team shape. Here's the mapping we use in real scoping calls:
| Your shape | What you genuinely need | What to skip |
|---|---|---|
| 1–3 people, mobile-first | Business number on the mobile app, professional greeting, voicemail-to-email, and an AI receptionist if calls arrive while you work. | Desk phones, queues, wallboards — genuinely unnecessary at this size. |
| 4–10 people, one site | The above plus an auto attendant, ring groups, and time-based routing for evenings and holidays. | Contact-centre features. A simple menu beats a complex one — two options, not seven. |
| 10–30 people, departments forming | Queues for busy teams, reporting so missed calls become visible, CRM screen-pops, and recording where conversations carry weight. | Per-feature à-la-carte pricing — at this size you want it bundled per user. |
| 30+ or multi-site | Everything above across sites on one system: inter-site overflow, wallboards, reception console, per-site reporting, and serious connectivity underneath. | Separate systems per site — the single-platform approach is the entire advantage. |
The recurring mistake in both directions: small teams over-buying enterprise features they'll never configure, and growing businesses under-buying and drowning in missed calls a queue would have caught. Match the shape, and the price usually surprises pleasantly.
The real total cost — including the lines nobody quotes
Per-user monthly pricing is only the headline. A truthful comparison between quotes checks six lines. Calls: are UK landline and mobile minutes inclusive, or does "from £X" hide per-minute billing that doubles the real cost? Handsets: bought, rented, or unnecessary (apps are free — many teams need fewer desk phones than they think)? Numbers: is porting your existing number included, and what do extra DDIs cost? Features: is call recording, the auto attendant, voicemail-to-email included — or a per-feature toll? Setup and training: included, or a surprise line on invoice one? Exit: what does leaving cost, and is the contract auto-renewing into another long term while you weren't looking?
Two structural truths help you negotiate. First, the underlying cost of cloud calling has fallen for a decade — a quote materially above market is margin, not technology. Second, the cheapest quote with per-minute calls, rented handsets and a punitive exit clause is routinely the most expensive over three years. Run every quote through our savings calculator and the arithmetic settles it. And for the deeper cost breakdown by system type, see the phone system cost guide.
Ten questions that expose a bad provider before you sign
Ask these of every provider — us included — and the pretenders eliminate themselves. One: will you test my broadband before installation? (If no, they're shipping boxes, not engineering calls.) Two: exactly what happens to my calls if my internet fails? (The answer should be automatic mobile failover, described specifically.) Three: who ports my numbers and what happens if it goes wrong? Four: is call recording, and its storage, included or extra? Five: can I change my own greetings and routing, or is every tweak a support ticket? Six: where is support based and when is it staffed? Seven: what does adding a user cost mid-contract? Eight: show me the exit terms in writing. Nine: what's included for training my team? Ten: can I speak to a customer like me?
Question ten does the most work. Any provider proud of their service produces a reference within a day; the ones who can't have told you everything. Our answers to all ten live across this site in writing — including the comparison hub where we put ourselves against every major alternative, which is not something a company with weak answers builds.
The first 90 days: what a good rollout looks like
Week one is configuration and porting paperwork: greetings recorded, call flows built to how you actually work (not a template), apps installed, and the number-port submitted — with your old service untouched until port day. Weeks two to four are live running with attention: the port completes in minutes on the agreed day, the team gets shown the three things they'll use daily (transfer, voicemail, the app — training beyond that is theatre), and early friction gets tuned out: the menu option nobody picks, the ring time that's a beat too long. Days 30–90 are where the system starts paying: the first missed-calls report usually surprises, staffing or routing adjusts to the actual pattern, and features you deferred — recording, CRM pops, the AI backstop — switch on now that the foundations are boring.
The metric that matters at day 90 isn't uptime — that should be a given — it's answered percentage. If it isn't visibly higher than before the switch, the system was installed but not designed. That's the difference you're paying a proper provider for.
Frequently asked questions
What’s the best business phone system for a small business?
For most small businesses, a hosted VoIP / cloud system is best — low cost per user, no hardware, and full features. We size it to your team.
Do I have to switch before 2027?
Yes — the PSTN and ISDN network switches off by January 2027, so any system relying on those lines must move to internet-based calling before then.
Can I keep my phone number?
Almost always — we port your existing numbers across so customers notice no change.
How long does installation take?
New cloud setups can be live within the hour; porting existing numbers takes a little longer and is scheduled to avoid disruption.
Should a small business get desk phones or just use the apps?
Most small teams now run mostly on apps — the business number on mobiles and laptops — with desk phones only where they earn a place: reception, a busy desk, a kitchen wall. Apps are free with the system, so start lean; adding a handset later takes minutes.
How long does switching phone systems take?
Configuration takes days; the number port is the pacing item — typically about a week for a single number, two to four for complex multi-line ports. Your old system keeps working until the moment of port, so there's no gap.
What's the difference between VoIP, hosted VoIP and a cloud PBX?
VoIP is the technology (calls over the internet); hosted VoIP is that technology delivered as a service; a cloud PBX is hosted VoIP with the full call-handling toolkit — menus, queues, reporting. In practice they're points on one spectrum, and the right question is which features your team needs, not which label.
Can we keep our phone number if we move office or city?
Yes — once ported to a cloud system your number lives independently of any address. Move from Wolverhampton to Birmingham and the 01902 number your customers know comes with you.
Is an AI receptionist worth adding to a phone system?
If calls arrive when nobody can answer — after hours, lunchtimes, all-hands-busy — yes, and measurably: it books and captures what voicemail loses. If your phone genuinely never rings unattended, skip it. The missed-calls report tells you which business you are.
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