Microsoft Teams Phone vs Direct Routing: which is right for your UK business?

Many UK businesses already use Microsoft Teams for chat and meetings, so turning it into the company phone system is a natural next step. With the PSTN switch-off on 31 January 2027, plenty of firms are making that decision now.

The confusing part is the language. "Teams Phone" and "Direct Routing" are often presented as rivals, but they are not quite the same kind of thing. This guide explains the choices in plain terms, so you can pick the one that fits your business.

First, a quick definition: what Teams Phone is

Teams Phone Standard is an add-on licence that gives Teams phone system features such as voicemail, call forwarding, transfers, auto attendants, call queues and caller ID. On its own, it does not connect you to the outside world. To call ordinary phone numbers, every Teams Phone user also needs a way to reach the public phone network.

Microsoft offers four ways to do that:

• Microsoft Calling Plans: Microsoft acts as your phone company.
• Operator Connect: a Microsoft-certified operator provides your numbers and calls, connected to Teams for you.
• Teams Phone Mobile: your mobile SIM number is also your Teams number, through a participating mobile operator.
• Direct Routing: you connect Teams to the carrier of your choice through a certified session border controller (SBC).

So the real question is not "Teams Phone or Direct Routing". It is "which way should our Teams Phone users connect to the phone network?" You can also mix options in one organisation, for example Calling Plans for a small branch and Direct Routing for a head office.

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Option 1: Microsoft Calling Plans

Calling Plans are the simplest route. Microsoft supplies the numbers, the calls and the support. They are available to UK organisations, with Domestic, International and Pay-As-You-Go plans.

Things to know for the UK, from Microsoft's UK number guidance:

• New numbers take up to 4 business days if available, or up to 90 business days if they must be ordered.
• Mobile numbers are not available, and non-geographic numbers are limited.
• Porting existing UK numbers to Microsoft takes around 12 to 30 business days and needs a signed Letter of Authorisation.
• Partial porting is not supported for UK numbers. If you want to keep some numbers with your current provider, plan carefully.

Calling Plans suit smaller organisations with straightforward needs that want one supplier and minimal setup.

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Option 2: Operator Connect

Operator Connect sits between the two extremes. A Microsoft-certified operator provides your phone service, and you switch it on and assign numbers from the Teams admin centre. Microsoft describes it as a good choice "when you want a managed PSTN solution without deploying and maintaining your own Session Border Controllers".

The operator is responsible for connectivity, number provisioning and porting, and call-related support. You can check which operators serve the UK in Microsoft's Operator Connect directory. It is a fair option to consider if your preferred carrier takes part in the programme.

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Option 3: Direct Routing

Direct Routing connects Teams Phone to any carrier through a supported SBC "procured, installed, and managed by you, your integrator, or a Direct-Routing-as-a-Service (DRaaS) provider". It offers the most control and flexibility.

Microsoft says Direct Routing is a good fit for organisations that:

• have an existing carrier relationship,
• need to integrate third-party phone systems or analogue devices,
• need advanced call routing, or
• want greater control over their telephony.

For UK businesses, that often means keeping a SIP trunk supplier you are happy with, connecting door entry or analogue devices, or running Teams alongside another phone system during a phased move. See our Microsoft Teams Direct Routing page for how NETON delivers it.

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When do you need an SBC?

This is the simplest way to separate the options:

• Calling Plans: no SBC needed. Microsoft provides the connection.
• Operator Connect: no SBC for you to deploy. The operator manages the connection.
• Direct Routing: yes, always. Microsoft requires a certified SBC and only supports Direct Routing with certified devices.

The SBC can be a physical box, a virtual machine or a hosted service. Setting it up involves a public IP address, a trusted certificate, a domain verified in Microsoft 365 and the right firewall rules, all listed in Microsoft's planning guide. Microsoft's certified list includes products from AudioCodes, Ribbon and TE-SYSTEMS (anynode), all of which NETON supplies. Our SBC page explains the choices.

Even if you mainly use Calling Plans or Operator Connect, Microsoft notes that a common pattern is to add Direct Routing for analogue devices or calls to third-party phone systems.

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Costs: what you are actually paying for

Prices change and vary by agreement, so we will not quote figures here. Check Microsoft's current pricing for Teams Phone and Calling Plans for the UK. The cost structure looks like this:

• All options: a Teams Phone licence for each user, on top of a qualifying Microsoft 365 or Teams plan.
• Calling Plans: a Microsoft Calling Plan per user, or a Teams Phone with Calling Plan bundle.
• Operator Connect: the operator's charges for numbers and calls.
• Direct Routing: your carrier's charges for numbers and calls, plus the SBC (bought, virtual or hosted) and its setup and support.

Direct Routing has more parts, but it lets you choose your carrier and call tariffs. Calling Plans have fewer parts, but you take Microsoft's terms. Compare the total cost over two or three years, including support time, rather than just the monthly licence line.

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Keeping your UK numbers

Losing a well-known number is bad for business, so check this early.

• With Calling Plans, you port numbers to Microsoft using its porting wizard. Remember that partial porting is not supported in the UK.
• With Operator Connect, the operator handles porting.
• With Direct Routing, numbers sit with the carrier you choose, so you port them to that carrier or keep them where they are if your current supplier offers SIP trunks.

Whichever route you choose, the details on your porting request must match your current provider's records exactly, or it may be rejected. NETON can supply UK numbers and SIP trunks for Direct Routing.

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Another route: Wildix alongside Teams

If you want Teams for collaboration but a dedicated business phone system behind it, Wildix offers teams4Wildix. Wildix says it lets Teams users make and receive calls through a Wildix PBX without additional Microsoft licences, using a Wildix tab in Teams. Calling from the Teams dial pad itself is also possible, but Wildix notes this needs Microsoft Teams Phone licences and extra configuration. Learn more about Wildix and x-bees.

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Which should you choose?

• Calling Plans if you are small, want one supplier and are happy with Microsoft's number and porting rules.
• Operator Connect if your preferred operator takes part and you want a managed service without an SBC.
• Direct Routing if you want to choose your carrier, connect analogue or other phone systems, or need flexible routing.

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The four options at a glance

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Frequently asked questions

Is Microsoft Teams Phone available in the UK?

Yes. Microsoft lists Calling Plans for UK organisations, Direct Routing works with the UK carrier of your choice, and Microsoft's Operator Connect directory shows which operators serve the UK.

Do I need a session border controller for Microsoft Teams calling?

Only for Direct Routing, which requires a Microsoft-certified SBC. Calling Plans and Operator Connect do not need you to deploy one.

Can I keep my existing UK business numbers on Teams?

Usually, yes. You can port them to Microsoft, to an Operator Connect operator, or to the carrier behind your Direct Routing setup. Note that Microsoft does not support partial porting of UK numbers into Calling Plans.

Is Direct Routing cheaper than Calling Plans?

It depends on your users, call volumes and carrier. Direct Routing adds SBC costs but lets you choose your carrier tariffs, so compare the total cost over the contract term.

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Sources

1. PSTN connectivity options — Microsoft Learn — 2026
2. Microsoft Teams add-on licensing — Microsoft Learn — 2026
3. Calling Plans for Microsoft 365 — Microsoft Learn — 2026
4. Phone number management for the United Kingdom — Microsoft Learn — 2026
5. Plan for Operator Connect — Microsoft Learn — 2026
6. Operator Connect directory — Microsoft — 2026
7. Plan Direct Routing — Microsoft Learn — 2026
8. Session Border Controllers certified for Direct Routing — Microsoft Learn — 2026
9. Microsoft Teams Phone and calling — Microsoft — 2026
10. teams4Wildix — Wildix — 2026
11. Openreach warns businesses: just six months left before the UK's old phone network is switched off — Openreach — 2026