In short: Business phone systems come in four main forms: an on-premise PBX connected by SIP trunks, a hosted or cloud phone system, Microsoft Teams Phone, or a carrier service such as BT Cloud Voice. The right choice depends on how your people work, what you already own, your call handling needs and the contract terms on offer.
The four ways to run a business phone system
Almost every option on the UK market falls into one of these four groups. Each can work well; the question is which suits you.
| Option | What it means | Often suits | Watch for |
|---|---|---|---|
| On-premise PBX on SIP trunks | You own the phone system, on site or in your own cloud, and connect it to the network over SIP | Organisations with a supported system, specific integrations or a need for local survivability | Hardware lifecycle, patching and who supports it |
| Hosted or cloud phone system | The provider runs the phone system; you use desk phones and apps (for example Forever UC, hosted 3CX or Webex Calling) | Most organisations, especially multi-site and hybrid teams | Connectivity quality and the contract terms |
| Microsoft Teams Phone | Calling inside Teams, with a Calling Plan, Operator Connect or Direct Routing | Organisations that already live in Microsoft 365 and Teams | Licensing for every user and shared device |
| BT Cloud Voice | BT's own cloud phone system | Organisations wanting BT for lines, broadband and phones | Covered in depth on cloudvoice.cloud |
The detailed trade-offs are in hosted vs on-premise phone systems and cloud phone systems compared. This guide sticks to how to buy.
Start with how your people work
Before you look at any product, write down a short picture of how calls actually flow in your organisation. It will save you from paying for features you never use, or missing the one you cannot live without.
- Users and sites: how many people, how many offices, and who works from home or on the road
- Devices: who needs a desk phone, who is happy with a softphone app, and who needs a cordless DECT handset
- Answering: one reception, a menu, departmental hunt groups or proper call queues
- Microsoft 365: if staff already spend the day in Teams, Teams Phone or Forever Teams may be the natural fit
- Call centre needs: queues, wallboards, supervisors and reporting point towards a call centre phone system or cloud contact centre
- Recording and CRM: whether you must record calls, and whether calls should pop up in your CRM (CRM integration)
- Special lines: alarms, lifts, door entry, card terminals and faxes that still use analogue lines
Questions to ask any phone system supplier
These questions separate a fair deal from one that locks you in. Ask them of every supplier, including us, and get the answers in writing.
- Contract length and notice: how long is the minimum term, what happens at the end, and how much notice do you need to give?
- Number ownership: are the numbers assigned to your organisation, and will the supplier release them promptly if you leave?
- Porting out: is there a charge or delay for porting your numbers to another provider?
- Support hours and response: when can you raise a fault, how is it raised, and what response does the contract commit to?
- Call recording retention: if recording is included, how long are recordings kept, where are they stored and can you export them?
- Resilience: what happens if your internet connection or a site goes down? Can calls divert to mobiles or another site automatically?
- Handsets: are phones bought, leased or included, who owns them at the end, and will they work with another provider?
- Changes: are moves, adds and changes included, and how quickly are they made?
Cost: compare like with like
Phone system pricing is hard to compare because platforms charge in different ways: per user per month, per system per year, per channel, or per minute. A low headline licence can be offset by call charges, handset leases or set-up fees, and the reverse.
Ask every supplier to quote the same users, numbers, call volumes, handsets and term, and compare the total over the contract. Our guide to cloud phone system cost lists everything that drives the price and what to have ready. For any specific figure, ask us for a quote.
The PSTN and ISDN switch-off
Openreach is switching off the PSTN and ISDN networks on 31 January 2027, and new analogue and ISDN lines have not been sold nationally since 5 September 2023. If your current phone system relies on ISDN2, ISDN30 or analogue lines, you will need to move it to SIP trunks, a hosted system or Teams before then.
Use our PSTN switch-off checklist to audit every line, and see ISDN replacement options for the routes side by side. The full background is in the PSTN switch-off 2027 guide on cloudvoice.cloud.
A short decision checklist
- We know how many users, sites and simultaneous calls we need
- We know which users need desk phones, apps, Teams or cordless handsets
- We have listed our call flows: menus, groups, queues and out-of-hours rules
- We have checked our internet connection and network can carry voice well
- We have found every analogue and ISDN line, including alarms and card terminals
- We know whether we need call recording, CRM integration or contact centre reporting
- We have compared quotes on the same basis and read the exit terms
When you can tick most of these, contact us and we will recommend the options that fit, with the reasons.
Why choose your cloud phone system with Forever Systems
We are vendor-neutral. Forever Group supplies and supports several cloud phone platforms, so we recommend the one that fits how your organisation works rather than the one we happen to sell.
- Side-by-side comparison of hosted 3CX, Microsoft Teams Phone, Forever UC, Forever Teams and Webex Calling for your users
- Contact centre and call recording options matched to your call volumes and CRM
- Number porting, handsets and set-up handled for you, including the move off analogue and ISDN lines
- Connectivity checked so call quality is right from day one
- UK support for moves, adds, changes and faults
- For BT Cloud Voice, see our BT Business Partner site cloudvoice.cloud
We work with businesses, schools, charities and public sector organisations. We do not sell consumer phone services.
Want a vendor-neutral cloud phone system comparison and quote?
Tell Forever Systems what you need and we will come back to you by email with options, not a hard sell.
Contact usFrequently asked questions
Is a cloud phone system always better than an on-premise one?
Not always. A cloud system removes the hardware, patching and server room, and suits remote and multi-site working. An on-premise or self-hosted system can still make sense if you have recent investment, specific integrations or a need for calls to keep working locally if the internet fails. We will be honest about which suits you.
What is the best business phone system in the UK?
There is no single best system. Hosted 3CX, Microsoft Teams Phone, Forever UC, Webex Calling and BT Cloud Voice each suit different organisations. The best fit depends on your users, devices, call handling, Microsoft 365 use and budget. We compare them side by side for you.
Can I keep my number if I change phone system?
In most cases, yes. Ofcom rules require providers to support number porting, so geographic and non-geographic numbers can normally move with you. Your new provider requests the port using details from your current account.
Do I need new handsets?
Not always. Many IP desk phones can be re-provisioned for another platform, and many users can switch to softphone apps instead. Older digital or analogue handsets usually cannot connect to a cloud system directly. We check what you have before recommending anything.
How long are business phone system contracts?
Terms vary by platform and supplier, from monthly to several years. Forever UC contracts start from 12 months, for example, and 3CX licences are annual. Always check the minimum term, the notice period and the terms for porting your numbers out.