Teams Phone, 8x8 or 3CX: which suits a 20-person business?

What's the difference between them?

They're three different ways of buying the same thing: a cloud phone system that works on desk phones, laptops and mobiles, with your existing business numbers.

None of them is the "best" phone system. Each is the best fit for a different kind of 20-person business.

What would 20 users cost?

Illustrative monthly costs, not a quote. Microsoft prices are its UK list prices on an annual subscription, excluding VAT, as shown on Microsoft's website in September 2026. Handsets, set-up and out-of-bundle calls are extra.

Three things stand out.

Microsoft 365 licences don't include Teams Phone. Business Basic, Standard and Premium let staff call each other in Teams, but calling outside numbers needs a Teams Phone licence for each person who makes or takes phone calls.

3CX's free edition stops at 10 users. The 3CX free edition, hosted by 3CX, covers up to 10 users, so a 20-person business needs a paid edition. The upside is that 3CX charges by simultaneous calls, so adding a 21st or 31st person doesn't add a licence.

The crossover is around 30 users. In our experience, a system on SIP trunks (phone lines delivered over your internet connection), such as 3CX, usually becomes more cost-effective at around 30 users. At 20, price both. Our article on how much a business phone system costs explains the two pricing models in detail.

Which features matter at 20 people?

At this size, most businesses need the same core features. All three platforms do them. The differences are in how far each goes.

• A menu and out-of-hours routing. "Press 1 for sales", holiday messages and a different route after 5pm. All three include this. See IVR and auto attendants.
• Call queues. Callers wait in line rather than ringing out. Teams Phone includes call queues. 3CX has them on its PRO edition and above. 8x8 includes them, with more supervisor tools at X4. See call queues and wallboards.
• Mobile app. Your office number on your mobile, so calls from home or site look the same to callers. See business phone app and softphone.
• Call recording. For training, disputes and compliance. Recording depends on licence tier on every platform. See call recording.
• Reporting. Missed calls, answer times and busy periods. 3CX PRO includes scheduled reports and Power BI. 8x8 adds supervisor analytics at X4. See call reporting.

Where they separate is at the top end. If you might need a full contact centre later, with calls, email and chat routed together (omnichannel routing), quality management or secure card payments during calls, 8x8's contact centre licences go furthest. If you want AI call transcription or an AI receptionist, 3CX's AI Edition and 8x8's AI tools both offer it. See contact centre and AI receptionist and transcription.

Which suits which kind of 20-person business?

An office that lives in Teams. Accountants, consultancies and professional firms where everyone is at a laptop in Teams all day. Teams Phone keeps calls, chat and meetings in one app. Choose a Calling Plan for simplicity, or Operator Connect with 8x8 if you want a phone provider alongside Microsoft. See Microsoft Teams calling.

A team that handles lots of customer calls. A booking office, a service desk or a sales team where missed calls cost money. 8x8 fits here, with queues, wallboards and reporting, and a clear route to a contact centre as you grow.

A mixed team. An office of eight in Teams, a reception desk and a dozen people on site or in a warehouse. 3CX lets desk phones, the mobile app and Teams sit on one system, so only the Teams users need Teams Phone licences. 3CX connects to Teams through Direct Routing, and we confirm which 3CX edition you need for that in the review.

A team planning to grow. If you'll be 30 or 40 people within two years, 3CX on SIP trunks often gets cheaper per head as you grow.

What about the switch-off and moving numbers?

On the day this article is published, there are 83 days until Openreach closes the UK's analogue phone network on 31 January 2027. Whichever platform you choose, the move follows the same steps. Our article on what still needs to move before the PSTN switch-off covers the lines, alarms and devices that get forgotten.

Your existing numbers can almost always move to Teams, 8x8 or 3CX. The new system is set up and tested first, then the numbers are ported. Openreach schedules ports during the working day, between 9am and 5pm, for every provider. See number porting.

Two things to settle on any platform: record a 999 emergency address for every user and site, including home workers, and bar international and premium-rate calls unless someone needs them. Hacked phone systems are usually used to make expensive calls overnight. See phone system fraud prevention.

How Indigo does this. Indigo Unified Communications supplies and supports 8x8, 3CX and Microsoft Teams Phone from our Glasgow office. We provide Teams Phone licences and Calling Plans, Teams numbers through 8x8 Operator Connect, Direct Routing through 8x8 or 3CX, and Gamma SIP trunks for 3CX. Every review prices a fully hosted option and a SIP option side by side, and you get a written recommendation within 2 working days. New phones run alongside the old system until the numbers port, porting is included in set-up, and international and premium-rate calls are barred as standard. Business phone systems →

What to do next

1. List your 20 users in three groups: Teams all day, heavy phone users, and mobile or desk phone only.
2. Write down the features you need now and the ones you might need in two years, such as a contact centre.
3. Check your Microsoft 365 licences, so you know whether Teams Phone is an add-on for everyone or only some.
4. Take the free PSTN switch-off check to find every line and device that needs to move.
5. Book a free phone system review and get Teams Phone, 8x8 and 3CX priced on the same basis.