Can Teams Calling replace your phone system?

Summary: Microsoft Teams now powers more than 320 million users, with 80 million using Teams Phone and 20 million connected to the PSTN. This guide explains how Teams Calling replaces the PBX, extends communication through mobile, SMS, and contact center integrations, and how IT leaders can plan a smooth migration with the right partner.

Most organizations already use Microsoft Teams for chat, meetings, and collaboration. The next step for IT leaders is deciding whether Teams Calling can handle enterprise-grade voice.

Moving calling into Teams isn’t just a system change. It’s a chance to simplify operations, reduce vendor complexity, and manage communications under the same security and identity framework as Microsoft 365.

As of 2025, Microsoft Teams supports 320 million monthly active users, according to UC Marketing’s State of Microsoft Teams report. Within that, there are around 80 million Teams Phone users, and more than 20 million of them have full PSTN connectivity. The scale of this growth shows how quickly businesses are adopting Teams Calling as a core part of their unified communications strategy.

This guide explains how Teams Calling works, the key challenges in moving from a PBX, and how the right provider can help enterprises migrate with confidence and control.

How Teams Calling replaces the PBX

Teams Calling includes the call features enterprises expect — auto-attendants, hunt groups, voicemail, call transfer, and conferencing — all delivered through Microsoft’s cloud.

There are three main ways to connect Teams Calling to the PSTN:

• Microsoft Calling Plans — Best for smaller or single-region deployments. You buy numbers and calling minutes directly from Microsoft.

• Operator Connect — PSTN connectivity through certified carriers integrated into the Microsoft cloud, offering simple setup and reliable performance.

• Direct Routing — The most flexible model. It connects Teams Calling to your existing SIP trunks, SBCs, or global carriers for advanced routing and integration.

For global or complex environments, Operator Connect or Direct Routing typically provide the control and scalability that enterprises need. In many cases, a mix and match approach is preferred.

With the right design, Teams Calling can:

• Replace legacy PBX systems and centralize management under Microsoft 365

• Retain existing phone numbers through SIP trunk integration

• Support hybrid coexistence during staged migrations

• Extend unified policies and analytics across sites and users

The result is a single, cloud-managed voice environment that’s easier to maintain, secure, and scale.

Why enterprises are moving to Teams Calling

Replacing a PBX with Teams Calling is about simplifying communications, not just reducing cost.

• Unified management
  Voice, meetings, and messaging operate under one platform and identity.
• Less maintenance
  No PBX hardware or on-premises updates to manage.
• Global reach
  PSTN connectivity across more than 50 countries through certified partners.
• Built-in resilience
  Redundant, cloud-based architecture ensures business continuity.
• Consistent experience
  A single interface for calls, chat, and meetings on any device.

For IT leaders, Teams Calling delivers predictability, consistency, and operational control across regions.

What features does Teams Calling offer?

Teams Calling offers several critical phone system features that can help provide you with a high-quality experience for your customers.

For example, it can allow you to:

• Control hold music
• Provide auto-attendants for your customers, which help guide them through the correct menu options and even answer simple questions without having to connect to a live representative
• Forward calls or set up simultaneous rungs
• Share incoming calls between users
• Transfer to voicemail during a call
• Access multiple caller ID options
• Switch devices, so users can quickly transfer between devices while maintaining a smooth customer experience
• Block certain types of calls or block all calls but allow specific ones through
• Conduct video and voice calls with connected team members
• Deliver voicemails to the exchange mailbox at the same time a voicemail is delivered
• Utilize shared line appearance
• Configure incoming calls when a user is already in a call or a conference, based on the company’s unique needs and plans

These features can be incredibly beneficial, especially as your business grows and you have more incoming phone traffic. 

How to extend Teams Calling to get more from the platform

There’s far more to Teams Calling than the features you get out of the box. Most enterprises use it for standard voice and collaboration, but its full value comes from extending it. With the right integrations, Teams Calling can connect employees, customers, and partners more effectively across every device and location.

1. Mobile and SMS Integration

Work doesn’t stop at the desk. Esim solutions like Mobile Connect extend Teams Calling to employees’ mobile devices, enabling them to use their business number anywhere. It supports hybrid and BYOD environments while maintaining control through Microsoft 365 compliance policies.

Adding SMS capabilities opens another communication channel. Teams users can send and receive text messages from their main business number, improving responsiveness for customer updates and service alerts.

2. Legacy and Contact Center integration

Many enterprises still rely on SIP phones, paging systems, or analog devices. Teams Calling can integrate these through SIP trunks or gateways, allowing gradual modernization without replacing existing hardware.

For customer-facing operations, connecting a contact center — from built-in call queues to advanced third-party platforms — keeps all voice activity within one environment for simpler management and a consistent user experience.

3. Compliance and AI

Industries with strict regulations can add call recording and archiving tools to ensure compliant voice capture without disrupting workflows.

AI-drive features such as transcription, call summaries, and intelligent routing through Microsoft Copilot, further streamline operations by reducing manual effort and improving visibility across calls.

Common challenges in Teams Calling migrations

Moving to Teams Calling can be complex for global or hybrid environments. Common challenges include:

• Number management and porting: Coordinating across carriers and geographies.

• Emergency calling setup: Configuring location-based routing and compliance.

• Hybrid coexistence: Running Teams alongside PBXs during phased rollouts.

• Device readiness: Ensuring Teams-certified phones, headsets, and gateways are supported.

• Governance: Defining routing, recording, and retention policies for distributed users.

Each challenge can be solved with a well-structured plan and the right voice partner.

⬇️ Hear from Paul Cornish at Merlin Entertainments on how his team achieved a smooth and successful Teams Calling rollout

How to plan a smooth Teams Calling migration

Migrating voice to Teams touches more than the phone system. It affects identity management, user behavior, network readiness, and global compliance. Many deployments stall because they treat voice as a quick add-on rather than a structured transformation. A successful Teams Calling migration needs a clear framework that balances speed with control. Read our Migration Guide for the full framework.

1. Define your goals
   Clarify what success looks like — consolidation, cost control, or better governance.
2. Audit your voice environment
   Map existing PBXs, SIP trunks, and call flows. Identify any dependencies like analog lines or contact centers.
3. Roll out in phases
   Start with pilot users, validate performance, then expand regionally.
4. Maintain coexistence
   Run your PBX and Teams Calling in parallel until all users are migrated.
5. Prepare users
   Provide guidance and training to drive confidence and adoption.
6. Work with experts
   Choose a Teams-certified partner with experience in global deployments and compliance management.

Deploying Teams Calling across a global enterprise requires specialist experience in connectivity, regulation, and architecture.

Pure IP delivers enterprise-grade Teams Calling with global PSTN access, certified SBCs, and full managed service support. Our specialists design and manage Teams Calling environments across 80+ countries, integrating SIP, UCaaS, and hybrid systems at scale.

Ready to plan your migration? Connect with a Pure IP voice expert to evaluate your environment and design your Teams Calling roadmap.