Microsoft Teams Phone Licensing Guide: Enterprise Voice Costs and PSTN Options

The Three-Layer Teams Phone Licensing Model

Microsoft Teams Phone System costs $8/user/month as a standalone add-on — but enterprise buyers rarely pay just that. Add PSTN connectivity, audio conferencing, and compliance recording, and the total per-seat cost for an enterprise voice deployment typically runs $20–35/user/month before negotiation. Most large organisations are paying for all three licence layers without fully understanding what each one costs or where the negotiation levers sit.

Layer one is the Phone System licence. This is the PBX engine inside Microsoft Teams that enables enterprise voice features including call queues, auto attendants, voicemail, call forwarding, and integration with session border controllers. Phone System is included in M365 E5 at no additional cost. For M365 E3 and below, it requires a separate Teams Phone add-on at $10 per user per month.

Layer two is PSTN connectivity. Phone System enables the PBX features, but it cannot make or receive calls to the public telephone network without a PSTN connectivity solution. Organisations choose between three models: Microsoft Calling Plans (Microsoft provides the carrier service directly), Operator Connect (a Microsoft-certified telecom operator provides PSTN access through the Teams Admin Center), or Direct Routing (the organisation connects its own Session Border Controller and SIP trunk to Teams Phone). Each model has different economics, different operational complexity, and different suitability profiles by organisation size and geographic footprint.

Layer three is the call plan or usage agreement. For Microsoft Calling Plans, this is a domestic or international minute bundle. For Operator Connect and Direct Routing, it is the commercial agreement with the carrier or SIP trunk provider. This layer is where the largest cost differences materialise at scale — and where the most negotiating leverage resides for enterprise buyers.

Teams Phone System Licence: What It Provides and When You Need It

The Phone System licence enables enterprise-grade telephony within Microsoft Teams. Key capabilities include auto attendant (automated call routing by time of day, business unit, or IVR menu), call queues (ACD-style queuing with agent assignment and overflow routing), direct inward dialling (DID) number assignment to individual users, voicemail with transcription, call recording (with compliance recording add-on), and integration with certified Session Border Controllers for Direct Routing deployments.

Phone System in E5 vs E3 Estates

For organisations on M365 E5 ($60 per user per month list), Phone System is included and no add-on is required. This is a meaningful E5 benefit that should be factored into any E3 versus E5 cost comparison for organisations that intend to deploy Teams Phone. At $10 per user per month for the Phone System add-on, the E5 premium over E3 ($21 per user per month) is effectively offset by approximately 50 percent by the included Phone System for any user who requires enterprise voice.

For E3 organisations, the Teams Phone add-on at $10 per user per month should be negotiated as a line item within the EA alongside the base plan SKUs. Standard EA discounts of 10 to 20 percent apply to add-ons, and organisations that bundle Teams Phone commitments into the broader EA renewal — alongside commitments to Copilot, Defender, or Teams Rooms — typically achieve better pricing than those who negotiate add-ons in isolation.

Who Needs a Phone System Licence

Not every user in the organisation requires Teams Phone. The licence should be assigned only to users who need to make or receive PSTN calls (external calls to phone numbers). Users who communicate exclusively via Teams-to-Teams calls, video meetings, and chat do not require the Phone System licence. In typical enterprise deployments, 60 to 80 percent of users require PSTN calling, while the remaining 20 to 40 percent can be served by Teams without the Phone System add-on. Licensing selectively — rather than applying Phone System across the entire estate — reduces the add-on cost proportionally.

PSTN Connectivity Option 1: Microsoft Calling Plans

Microsoft Calling Plans are the simplest PSTN connectivity option — Microsoft acts as the carrier, providing phone numbers, minute bundles, and all PSTN infrastructure directly through the Microsoft 365 Admin Center. There is no SBC to deploy, no carrier relationship to manage, and no SIP trunk to configure. Number porting from existing carriers, call quality management, and emergency services integration are all handled by Microsoft.

Calling Plan Pricing in 2026

Microsoft Calling Plan pricing varies by country and by minute bundle. In the United States, domestic Calling Plans are priced at approximately $12 to $15 per user per month for domestic calls, with international add-ons available separately. In the UK, domestic Calling Plans run approximately £9 to £12 per user per month. For organisations operating across multiple countries, each country requires separate Calling Plan subscriptions at country-specific rates, and not all countries where Microsoft 365 is available have Microsoft Calling Plans available — coverage gaps require alternative connectivity solutions for those markets.

When Calling Plans Make Sense

Microsoft Calling Plans are the appropriate choice for organisations with fewer than 200 calling users, no existing carrier contracts with significant remaining term, geographic concentration in countries where Calling Plans are available with good coverage, and IT teams with limited SBC or telephony infrastructure experience. For these organisations, the administrative simplicity and single-vendor support relationship justify the premium pricing relative to Direct Routing or Operator Connect.

When Calling Plans Are the Wrong Choice

For organisations with 500 or more calling users, international footprints across multiple countries, existing SBC infrastructure, or existing carrier contracts, Microsoft Calling Plans are typically significantly more expensive than the alternatives. At 500 users in the US, Microsoft Calling Plans cost approximately $75,000 to $90,000 annually for PSTN access alone — before the Phone System licence cost. Direct Routing via a competitive SIP trunk provider commonly reduces this to under $20,000 annually for equivalent calling volumes, representing savings of $55,000 to $70,000 per year for PSTN connectivity only.

PSTN Connectivity Option 2: Operator Connect

Operator Connect is Microsoft's managed carrier integration programme, launched in 2021 and now the preferred PSTN connectivity model for mid-market enterprises. Microsoft-certified telecom operators — including major carriers in each country — provide PSTN connectivity directly through the Microsoft Teams Admin Center, without requiring the organisation to deploy or manage a Session Border Controller.

How Operator Connect Works

The organisation selects a Microsoft-certified Operator Connect carrier from the Teams Admin Center, establishes a commercial agreement directly with the carrier, and assigns numbers through the Admin Center interface. The carrier operates the SBC infrastructure on the organisation's behalf, and Microsoft's Admin Center provides unified management of numbers, users, and calling policies across the Teams estate. Call quality data flows through the Teams Call Quality Dashboard, giving IT the same visibility as Calling Plans without the carrier management overhead of Direct Routing.

Operator Connect Pricing

Operator Connect pricing varies significantly by carrier and country. Typically, Operator Connect delivers 30 to 50 percent lower PSTN connectivity costs compared to Microsoft Calling Plans, with the advantage that carrier pricing is negotiable based on call volume, term commitment, and overall carrier relationship. For organisations with 200 to 1,000 calling users, Operator Connect represents the optimal balance of cost, operational simplicity, and geographic coverage.

Geographic Coverage Advantage

One of Operator Connect's critical advantages over Microsoft Calling Plans is geographic coverage. Microsoft Calling Plans are available in approximately 33 countries. The Operator Connect ecosystem, through multiple carriers, covers substantially more markets — making it the preferred solution for genuinely multinational organisations where Microsoft Calling Plans would leave coverage gaps requiring additional telephony infrastructure in uncovered countries.

PSTN Connectivity Option 3: Direct Routing

Direct Routing connects Microsoft Teams Phone System to any PSTN carrier or SIP trunk provider via a Session Border Controller deployed by or on behalf of the organisation. It is the most flexible and typically the lowest-cost PSTN connectivity option for large enterprises, at the cost of greater deployment and operational complexity.

How Direct Routing Works

A certified SBC (Session Border Controller) from vendors including AudioCodes, Ribbon, Oracle (ACME Packet), or Cisco acts as the interface between the Microsoft Teams Phone System and the carrier's SIP trunk. The SBC handles protocol translation, media encryption, survivability (on-premises calling if internet connectivity is lost), and integration with legacy on-premises PBX infrastructure during migration periods. The organisation negotiates directly with a SIP trunk provider for PSTN access, independent of Microsoft.

Direct Routing Economics

The cost advantage of Direct Routing materialises through carrier pricing flexibility. SIP trunk providers compete aggressively for enterprise voice traffic, and per-minute rates at enterprise scale are a fraction of Microsoft Calling Plan rates. A 1,000-user organisation making average call volumes of 2 minutes per user per day generates approximately 20,000 minutes of PSTN traffic per day. At Microsoft Calling Plan rates, this costs approximately $150 to $200 per day. At competitive SIP trunk rates via Direct Routing, the equivalent traffic costs $20 to $50 per day — a saving of $47,000 to $65,000 annually on PSTN usage alone before factoring in the SBC amortisation.

For organisations with existing SBC infrastructure (deployed for legacy on-premises Lync, Skype for Business, or third-party PBX migrations), Direct Routing adds minimal incremental cost since the SBC infrastructure already exists. The incremental cost is primarily SIP trunk configuration and Teams Phone licences.

Direct Routing Operational Considerations

Direct Routing requires internal or managed service capability to deploy, configure, and maintain the SBC infrastructure. Microsoft does not provide SBC support — the SBC vendor and SIP trunk provider support their respective components, and the organisation is responsible for overall integration management. For organisations without telephony infrastructure expertise, a managed Direct Routing service from a Microsoft partner is typically more appropriate than self-operated Direct Routing. Managed Direct Routing services from specialist providers typically cost $2 to $5 per user per month for the managed SBC service, while still delivering substantial savings versus Microsoft Calling Plans.

Audio Conferencing: The Hidden Cost

Audio Conferencing is separate from Teams Phone and provides dial-in phone access to Teams meetings for participants without internet access or Teams clients. It is included in M365 E5 but requires a separate add-on ($4 per user per month) for E3 and below. For organisations running Teams as their primary meeting platform, Audio Conferencing is typically required for executives, external participants, and users in regions with unreliable internet connectivity.

Audio Conferencing is frequently overlooked in Teams Phone cost models. An organisation deploying Teams Phone on E3 across 1,000 users may need both the Phone System add-on ($10 per user per month) and the Audio Conferencing add-on ($4 per user per month) for all or most users, adding $14 per user per month in add-on costs before PSTN connectivity. This is a meaningful consideration in the E3 versus E5 cost comparison for telephony-intensive deployments.

Teams Phone and the E5 Bundle Decision

For organisations planning to deploy Teams Phone, the E3 plus add-ons versus E5 arithmetic deserves careful analysis. E5 at $60 per user per month includes Phone System and Audio Conferencing (combined add-on value of $14 per user per month) alongside E5 Security and E5 Compliance capabilities. E3 at $39 per user per month plus Phone System ($10) plus Audio Conferencing ($4) totals $53 per user per month — only $7 below E5 list price, without the security and compliance capabilities that E5 provides.

For users in roles where E5 security (Defender for Endpoint P2, Entra ID P2, advanced compliance) is genuinely required, the incremental cost from E3 plus telephony add-ons to E5 is minimal. The case for E5 is strongest for knowledge workers who need both full telephony and advanced security. The case for E3 plus selective add-ons is strongest for users who need telephony but do not require E5 security — typically operational and support roles.

Negotiating Teams Phone in the EA

Teams Phone licensing should be negotiated as part of the broader Microsoft EA renewal, not as a standalone procurement. Several specific negotiation levers apply.

First, bundle the Teams Phone commitment into the total EA contract value. A large Teams Phone deployment increases the total EA TCV, which Microsoft's deal desk uses to justify enhanced overall discounts. Use the Teams Phone volume commitment to negotiate incremental discounts on the base M365 plan SKUs.

Second, negotiate multi-year pricing for add-ons. Teams Phone add-on pricing can be locked for the EA term, protecting the organisation against the price increases that Microsoft has implemented progressively across M365 add-ons since 2022.

Third, if migrating from an existing carrier or on-premises PBX, create competitive tension by timing the Teams Phone commercial discussion to overlap with carrier renewal negotiations. If the incumbent carrier is aware of the Teams Phone evaluation, they will typically offer significant retention pricing — improving the baseline against which Teams Phone must compete.

Fourth, negotiate PSTN connectivity separately from the Microsoft licence. Even if Microsoft Calling Plans are the chosen connectivity model, the per-minute rate, minute bundle size, and country coverage terms within Calling Plans can be negotiated within a large EA — something most organisations do not attempt because they assume Calling Plan rates are fixed.

Teams Phone Migration: Avoiding Common Cost Traps

Organisations migrating to Teams Phone from legacy on-premises PBX or third-party UCaaS platforms face several cost traps that drive total migration cost above initial estimates.

The most common trap is retaining legacy PBX infrastructure in parallel during migration, creating double-running costs for PSTN connectivity, support contracts, and hardware maintenance. Migration projects that do not have a clear cutover plan and aggressive number porting schedule extend parallel running periods, which can add hundreds of thousands of dollars in unnecessary costs to large enterprise migrations.

The second trap is miscounting the Phone System licence requirement. During migrations, organisations frequently licence all users for Phone System from day one, before legacy systems are decommissioned. Licence consumption should be staggered to align with actual cutover waves, not with project kick-off dates.

The third trap is choosing Microsoft Calling Plans for a large deployment because it is technically simpler to implement, without modelling the multi-year cost difference against Direct Routing or Operator Connect. A three-year TCO analysis almost always favours the more operationally complex option for organisations above 500 calling users, when the PSTN connectivity savings are properly accounted for.