VoIP Phone Systems for Small Businesses: How They Work and What They Cost

Last updated: 12 November 2026

For years, a business phone system meant a box in a cupboard, a bundle of phone lines and an engineer to change anything. That model is ending. The UK’s old copper phone network is being switched off on 31 January 2027, and Openreach has been clear the date won’t move again. Every business still using traditional lines needs to be on a digital alternative by then.

For most small businesses, that alternative is a VoIP phone system. This guide explains how VoIP works, what you get, what it costs, and how to switch without disrupting your calls.

VoIP at a Glance

What it is: a phone system that carries calls over your internet connection instead of a traditional phone line.
Why now: the traditional phone network (PSTN) closes on 31 January 2027.
What you get: your existing numbers, desk phones or apps, call routing, voicemail to email, recording and reporting.
What it costs: usually a monthly fee per user, plus any desk phones you choose and, sometimes, a better internet connection.
What matters most: a stable internet connection, ideally with a backup.

What VoIP Actually Is

VoIP stands for Voice over Internet Protocol, which simply means your calls travel as data over the internet, the same way email and video calls do. Most modern business VoIP is hosted, or “cloud”, telephony: the phone system itself runs in a secure data centre, and your phones, computers and mobiles connect to it over the internet.

To your customers, nothing changes. They ring the same number and reach the same people. Behind the scenes, though, there’s no phone system in a cupboard to maintain, and changes that used to need an engineer can be made in minutes from a web portal.

How a VoIP Phone System Works

Your numbers live in the cloud. Your existing numbers are moved to the VoIP provider and attached to your hosted phone system.
Your devices connect over the internet. Desk phones plug into your network, and staff can also use an app on their computer or mobile.
The system routes each call. Rules you set decide who rings, in what order, and what happens out of hours or when everyone is busy.
You manage it online. Adding a new starter, changing opening hours or recording a new greeting is done through a portal, not a site visit.

Why the PSTN Switch-Off Matters

The Public Switched Telephone Network (PSTN) is the old copper network that traditional phone lines and ISDN phone systems run on, and Openreach is retiring it on 31 January 2027. It isn’t only phones that are affected: alarms, lift lines, card machines and other equipment that dials out over a phone line need checking too. Our article on what your business needs to do before the switch-off covers what could stop working and what to check. This guide focuses on the phone system you move to.

What You Get With a Business VoIP System

A good cloud phone system does far more than a traditional line ever could, usually at no extra cost:

Keep your numbers, and add new local or national numbers easily.
Answer calls anywhere, on a desk phone, a computer or a mobile app, using your business number rather than a personal mobile.
Call routing and ring groups, so calls reach the right team, with queues, menus and out-of-hours messages.
Voicemail to email, so messages don’t sit unheard.
Call recording, for training, disputes and compliance.
CRM integration, so a customer’s record appears when they call.
Live wallboards and reporting, showing missed calls, waiting times and busy periods.
Flexibility, to add or remove users as your team changes, and to connect multiple sites as one system.

What a VoIP Phone System Costs

VoIP is usually priced per user, per month, which makes costs predictable and easy to scale. When comparing quotes, look at the full picture:

Cost	What to check
User licences	The monthly fee per person, and exactly which features it includes
Calls	Whether UK landline and mobile calls are included, and the rates for anything that isn’t
Numbers	Any charge for moving your existing numbers or adding new ones
Hardware	Desk phones and headsets, which are optional if staff use apps
Internet connection	Whether your current connection is good enough, or needs upgrading or a backup line
Set-up and support	Who configures your call flows, trains your team and fixes problems

Compare the total against what you pay today, including line rental, ISDN channels, call charges and any maintenance contract on an old phone system. Many businesses find the move saves money as well as adding features.

What You Need for Good Call Quality

VoIP quality depends almost entirely on your internet connection and network. Before switching, it’s worth checking:

A stable connection, with enough upload capacity for the number of calls you make at once. Stability matters more than headline speed.
Router settings that prioritise voice traffic over downloads and backups.
Wired desk phones where possible, and good Wi-Fi coverage for anyone using apps on laptops or mobiles.
A backup connection, such as 4G or 5G failover, if your business can’t afford to lose the phones when the internet drops.

Our business connectivity service covers leased lines, broadband and automatic 4G and 5G failover, and our article on what happens when your phones go down explains why one supplier for both makes problems quicker to fix.

VoIP or Microsoft Teams Phone?

If your team already lives in Microsoft Teams, you can add phone calling to Teams itself, so calls arrive in the same app as your chats and meetings. That suits office-based teams who work mostly at their computers.

A dedicated cloud phone system tends to suit businesses with a busy reception, call queues, recording or reporting needs, or staff who work mainly from mobiles. Our Microsoft Teams Phone page explains the Teams option, and we can help you choose between them.

How to Switch Without Disruption

List every line and what uses it, including alarms, lifts, card machines and fax lines, not just the phones.
Check your internet connection, and add a backup line if the phones are critical.
Plan your call flows: who answers, in what order, and what happens out of hours.
Start moving your numbers early, as porting usually takes a couple of weeks.
Set up and test phones and apps before the numbers move.
Go live and train your team, usually in under an hour for most staff.

If you’re weighing it up, our article on moving to a cloud phone system covers the worries people usually have, and whether they’re justified.

Frequently Asked Questions

Can I keep my existing phone numbers if I move to VoIP?

Yes, in almost all cases. Your numbers are transferred from your current provider in a process called porting. It usually takes a couple of weeks, so it is worth starting early, and your old service keeps working until the moment the numbers move.

Will a VoIP phone system work if our internet goes down?

Calls can be diverted automatically to mobiles or another site, and staff can keep working on the mobile app over 4G or 5G. For businesses that rely on the phones, a backup internet connection that takes over automatically is the most reliable answer.

What happens to our alarm, lift line or card machine?

Anything that currently uses a traditional phone line needs checking before the switch-off, because it may stop working when the line is changed. Most can be moved to a digital line, a mobile SIM or the internet, but each one needs to be confirmed with its supplier.

How much internet bandwidth does a VoIP call use?

A standard-quality call uses around 100 kilobits per second in each direction, so even a modest business connection can carry many calls at once. Stability matters more than raw speed, which is why the connection and router setup are checked before you switch.

Do we need new desk phones?

Not necessarily. Many teams use the desktop and mobile apps with a headset instead. Where desk phones are needed, for example on a reception desk, VoIP handsets are supplied with the system, and some existing phones can be reused.

How CCSW Can Help

CCSW CallOne is our cloud phone system for businesses across Cardiff, South Wales and the UK. It includes mobile and desktop apps, call recording, CRM integration and live wallboards, from £12.61 per user per month (excluding VAT), with desk phones quoted separately.

Because we also provide managed IT support and business connectivity, we can look after your phones, internet connection and backup line together, on one invoice, with one team to call if anything goes wrong. We’ll also help you check every line and device before the switch-off, so nothing gets missed.

To talk through your options, get in touch or call 0333 014 4544. You can also get an instant estimate that includes cloud phones.