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Teams Phone for a Small Office: Calling Plan vs Operator Connect vs Direct Routing
Teams can replace a small office's phone system, but Teams on its own only calls other Teams users. To call regular phone numbers you need two things: Teams Phone, the phone system, and a way to connect it to the public phone network (PSTN). Microsoft offers four ways to make that connection. Here's what each one is, who it suits, and how I'd choose for a 5–50 person office.
The short answer
- Microsoft Calling Plan: Microsoft is your phone company. It's the simplest option if Calling Plans are sold in your country.
- Operator Connect: a Microsoft-certified phone carrier provides your numbers and calling, and you connect it from the Teams admin center. A good fit if you want a carrier's pricing or support, or a carrier you already use takes part.
- Teams Phone Mobile: a certified mobile operator makes a user's mobile number their Teams number too.
- Direct Routing: you bring any carrier through a Session Border Controller (SBC) that you, an integrator, or a hosted provider runs. Powerful, but rarely the right first choice for a small office without a voice partner.
These descriptions follow Microsoft's own summary of the four PSTN connectivity options (PSTN connectivity options). Microsoft also says you can use more than one option in the same tenant.
What you need in every case
Every option needs a Teams license plus Teams Phone. Microsoft describes Teams Phone Standard as an add-on that gives you the phone-system features: cloud voicemail, call forwarding, call transfer, auto attendants, call queues, and caller ID (Teams add-on licensing). Microsoft 365 Business Premium and E3 don't include Teams Phone. The licensing details are in Teams Phone licensing with Business Premium or E3.
The four options side by side
From Microsoft's comparison (PSTN connectivity options):
| Option | Who provides numbers, calling and support | What you need besides Teams Phone |
|---|---|---|
| Calling Plan | Microsoft | A Microsoft Teams Calling Plan license |
| Operator Connect | The certified operator | A contract with that operator |
| Teams Phone Mobile | The certified mobile operator | A subscription with that mobile operator |
| Direct Routing | Your carrier and you | A carrier contract and a certified SBC |
Option 1: Microsoft Calling Plan
- Microsoft says Calling Plans give you PSTN access, phone numbers, emergency screening in the U.S., and support from Microsoft, with a 99.999% reliability SLA (PSTN connectivity options).
- There are three types: Domestic, International, and Pay-As-You-Go. Microsoft says users in the same country on the same Calling Plan share a pool of minutes (Teams Calling Plans).
- Price: microsoft.com lists Teams Phone with Calling Plan (US) at $17.00 user/month and Teams Phone with domestic and international calling at $34.00 user/month, both paid yearly, and notes a separate Teams license is required (Microsoft Teams Phone, checked 2026-10-22). Check that page for current prices and your market.
- Keeping your number: you can port existing numbers to Microsoft. See Port your business number to Teams.
Option 2: Operator Connect
- Microsoft says the carrier has already done the integration work. You choose an operator, enable it in the Teams admin center under Voice > Operator Connect, and assign its numbers to users (Configure Operator Connect).
- Before you start, Microsoft lists: Teams Phone licenses for users, users in Teams Only mode, the right admin permissions, and a certified operator that serves your country (Plan for Operator Connect).
- Microsoft suggests comparing operators on country coverage, number availability and porting support, calling plans, and existing business relationships. Microsoft says PSTN access, numbers, support and SLA come from the operator, so pricing and support terms are the operator's.
Option 3: Teams Phone Mobile
Microsoft says Teams Phone Mobile lets a user's mobile SIM number also be their Teams number, through a certified mobile operator (PSTN connectivity options). It's worth asking about if your staff live on their mobiles and your mobile carrier offers it.
Option 4: Direct Routing
With Direct Routing you can use any carrier, connected through a certified SBC that's bought, installed, and managed by you, your integrator, or a Direct-Routing-as-a-Service provider (PSTN connectivity options). Microsoft says Direct Routing lets organizations keep existing carriers and integrate third-party phone systems, and its planning guide covers infrastructure, licensing, networking, SBC, and connectivity requirements (Plan Direct Routing). My view: for a small office this only makes sense if you have a voice partner who'll run it, or a requirement the other options can't meet, such as a carrier that isn't available through Operator Connect.
How I'd choose
- Check availability. Is a Calling Plan sold in your country, and which Operator Connect carriers cover you?
- Count how people call. Mostly inbound and local calls point toward a Domestic Calling Plan or an operator's equivalent. Lots of international calling changes the math, so compare plans.
- Decide who you want to call when the phones are down. With a Calling Plan it's Microsoft support. With Operator Connect it's the carrier.
- Plan emergency calling. Each option handles emergency addresses differently. Microsoft's emergency calling article explains how (Emergency addresses and call routing).
Once numbers are in place, the next steps are an auto attendant and call queue, then a check of your network using Teams call quality basics.
More in the Teams Phone series: Teams Phone licensing with Business Premium or E3 · Auto attendant and call queue setup · Port your business number to Teams · Teams call quality basics · Teams-certified headsets and desk phones. Choosing a Microsoft 365 plan first? See Business Premium vs E3.
Sources
- PSTN connectivity options (Microsoft Learn)
- Microsoft Teams add-on licensing (Microsoft Learn)
- Microsoft Teams Calling Plans (Microsoft Learn)
- Plan for Operator Connect (Microsoft Learn)
- Configure Operator Connect (Microsoft Learn)
- Plan Direct Routing (Microsoft Learn)
- Manage emergency calling (Microsoft Learn)
- Microsoft Teams Phone plans and pricing (Microsoft)
Where to buy: Teams Phone and Calling Plans from Microsoft on the Teams Phone page or through a Microsoft partner. Operator Connect pricing comes from each operator. These are ordinary links, not affiliate links.