You're already in Microsoft Teams all day—chats, meetings, files. Then a customer rings your 029 number, and someone digs out a mobile or walks to an old desk phone that isn't part of the same conversation.

Microsoft Teams calling (Teams Phone) puts proper inbound and outbound calls inside the Teams app, with a real UK number. For many Cardiff and South Wales businesses on Microsoft 365, that's appealing. The question is whether it's right for your team—or whether a dedicated cloud-based phone system still fits better.

What Microsoft Teams calling actually means

Teams on its own lets people call each other inside Teams. That isn't the same as ringing a customer's mobile or answering your published business number.

For normal telephone calls you need Teams Phone—Microsoft's cloud PBX features—plus a connection to the PSTN (the public phone network). Users need Teams Phone licensing and a separate PSTN option for external calling (Microsoft Learn: Teams Phone licensing; PSTN connectivity options).

Once live, staff can answer the main number or a direct dial from the Teams app; place outbound calls with your business caller ID; transfer, hold and forward; and use auto attendants and call queues. Certified desk phones are optional.

Three ways to connect Teams to the phone network

For most UK firms the practical choice is between three models (Microsoft Learn):

Microsoft Calling Plans

Microsoft is your phone operator. You buy Calling Plan licences (or a Teams Phone with Calling Plan bundle), Microsoft provides numbers and minutes, and you manage it in the Microsoft 365 admin centres.

Best when you want the simplest all-Microsoft stack. Calling Plans aren't always the cheapest once you scale, and some firms prefer a UK telecoms specialist for numbers and day-to-day voice support. We don't quote Microsoft list prices here—they change—so check the admin centre or your Microsoft partner.

Operator Connect

You work with a Microsoft-certified telecoms operator. They manage the PSTN side and the session border controllers; you enable them in the Teams admin centre and assign numbers to users. It's designed to be simpler than building Direct Routing yourself (Plan for Operator Connect).

Best when you want carrier-grade UK voice with a certified operator and prefer managing users and numbers in Teams.

Gamma is a participating Operator Connect provider (Microsoft marketplace listing and Gamma's Operator Connect programme announcements). As a Gamma Accredited Partner, we can talk through how Operator Connect sits with the rest of your telecoms if it's on your shortlist.

Direct Routing

You (or a partner) connect Teams Phone to a certified Session Border Controller (SBC) and bring your own SIP trunk. It's the most flexible option and often suits complex estates: analogue devices, contact centres, mixed PBXs or custom routing.

Best when you need advanced integration. Watch for more design and ongoing SBC care than Operator Connect—fine with the right partner, overkill for a small office that just wants numbers in Teams. Most small and mid-sized firms pick one primary model and stick to it.

Keeping your 029 number

Usually yes. With Calling Plans, Operator Connect or Direct Routing, existing geographic numbers can typically be ported. Customers keep dialling the same Cardiff number; Google listings and stationery don't need a reprint.

Porting isn't instant—plan it for a quiet day, test both ways first, and have a temporary divert ready. Our landline to VoIP guide covers how it works in practice.

When Teams calling suits a business—vs a dedicated cloud phone system

Teams Phone often fits when you're already deep in Microsoft 365, hybrid working matters, call volumes are moderate, routing is fairly standard, and you're happy managing licences in Teams. It's also a clean digital path off old ISDN or analogue lines ahead of the PSTN switch-off.

A dedicated cloud phone system often fits better when phones are mission-critical (busy reception, multi-site hunt groups, heavy recording), not everyone needs a full Microsoft 365 licence just to answer the phone, staff want simple desk phones more than a full Teams client, or you'd rather have one local partner for phones, broadband and Wi-Fi.

Our Gamma Horizon business phone systems are built for that second group. Horizon is £19.99 per user per month plus VAT, with the app included for handset, laptop or mobile. Many Cardiff firms run Horizon for phones and keep Teams for meetings and chat.

There's no universal winner—it depends on how your team takes calls. Our business phone system cost guide explains what goes into the price, whichever route you choose.

What you need: licences, headsets and broadband

Licences. Each user who needs their own number generally needs a qualifying Microsoft 365 / Teams base licence, Teams Phone (included in some higher plans such as certain E5 bundles; otherwise usually a Teams Phone Standard add-on), and a PSTN route—Calling Plan, Operator Connect or Direct Routing. Shared devices and call queues have their own patterns—check Microsoft's current licensing page before you order.

Headsets. A quiet headset with a noise-cancelling mic makes a bigger difference than most people expect. Certified Teams phones are optional. Brief training still helps for transfers and mobile hunt groups.

Broadband and Wi-Fi. Unstable Wi-Fi or a saturated upload shows up as choppy audio long before it shows in a speed test. For Teams calling—or any cloud phone system—use solid business broadband and office Wi-Fi. A free line check tells you what's available at your address.

The PSTN switch-off angle

The traditional UK phone network is being retired, with the industry aiming to complete the move away from analogue and ISDN by 31 January 2027. New analogue lines have already stopped being sold. If you're still on copper lines in Cardiff or South Wales, you need a digital plan—Teams Phone with a PSTN route, or a dedicated VoIP system such as Horizon.

Either path gets you off the old network. The switch-off is why many firms are reviewing phones now; it isn't by itself a reason to pick Teams over Horizon. See our PSTN switch-off guide for Cardiff businesses.

How we can help

Crystal Voice Data looks after business telecoms across Cardiff and South Wales. We're a Gamma Accredited Partner and an O2 Business Partner, designing business phone systems, broadband and Wi-Fi to match how you work.

Already on Microsoft 365 and weighing Teams Phone, Operator Connect or Horizon? Book a free phone line check or call 0333 5678 444. We'll look at how you take calls today, what licences you already own, and how to keep your 029 number.

FAQ

Do we need Microsoft Calling Plans if we use Operator Connect?

No. Calling Plans are Microsoft's own PSTN product. With Operator Connect or Direct Routing the certified operator (or your SIP provider) supplies the dial tone; you still need Teams Phone licensing for the PBX features.

Is Teams Phone the same as a Teams meeting dial-in number?

No. Audio Conferencing dial-in numbers let people join meetings by phone. Teams Phone is everyday business calling—your published numbers, queues and user extensions.

Can a small Cardiff business use Teams calling?

Yes, if you're already on Microsoft 365 and call handling is fairly simple. Smaller teams sometimes find a dedicated cloud phone system quicker day to day, especially if not everyone needs a full Teams licence. We're happy to compare both.

Will it work from home?

Yes—if home broadband is reliable and staff use a proper headset. Design call routing so the main number is still answered professionally outside the office.

What about alarms, lifts and door entry on old phone lines?

Those often need a separate digital plan; they don't move automatically when staff take calls in Teams. Flag every analogue device early.

Ready to talk it through? Contact us for a free phone line check, or ring 0333 5678 444.

Paul Ward, Crystal Voice Data