Unify vs Extend vs Connect: Which Teams Phone Extensibility Model Is Right For Me?

Teams Phone is no longer your basic calling add-on. The potential for Teams Phone is huge.

But here’s the reality..

Not every organization can squeeze their telephony requirements into Microsoft’s one-size-fits-all approach. 

That’s precisely why Microsoft introduced Teams Phone extensibility models. To give you the flexibility to integrate, enhance, or connect your existing systems with Teams in ways that actually make business sense.

The challenge? 

Choosing between Unify, Extend, and Connect models. Honestly, it’s a lot to unpack.

This comprehensive guide cuts through the technical jargon to help you make an informed decision that aligns with your business needs, budget, and technical capabilities.

What Is Teams Phone Extensibility?

Teams Phone extensibility represents Microsoft’s acknowledgment that enterprises don’t operate in cookie-cutter scenarios. 

It’s the framework that allows external telephony systems, contact center platforms, and custom applications to integrate with Microsoft Teams at varying levels of depth and complexity.

Think of it as Microsoft offering three different doorways into the Teams Phone ecosystem:

• Unify: The full migration path using native Azure Communication Services
• Extend: The hybrid approach that bridges your existing infrastructure with Teams
• Connect: The lightweight integration for basic interoperability

Each model serves distinct business scenarios, comes with different technical requirements, and carries varying levels of complexity and cost.

High-Level Overview of Unify vs Extend vs Connect

Before diving into the technical details, here’s how the three extensibility models compare at a glance:

The Unify Model: Native Azure Communication Services Integration

How It Works

The Unify model represents Microsoft’s most sophisticated extensibility approach, built entirely on Azure Communication Services (ACS). 

Instead of bolting external systems onto Teams, Unify creates native contact center applications using the same underlying infrastructure that powers Teams Phone itself.

This model leverages:

• ACS Call Automation SDK for programmatic call control
• ACS Calling SDK for real-time communication capabilities
• Azure AI Services for intelligent customer interactions
• Teams Phone extensibility APIs for seamless integration

Architecture Deep Dive

Under the hood, Unify applications share the same 99.999% uptime infrastructure as Teams Phone. 

Your contact center solution doesn’t just integrate with Teams—it becomes part of the Teams Phone ecosystem. Calls flow through the same Azure infrastructure, using the same global network that Microsoft relies on for its own services.

The technical architecture eliminates the multiple API hops that plague other integration models. Instead of routing calls through Graph APIs and then back to Teams, everything happens within the ACS environment, reducing latency and improving reliability.

PSTN Connectivity Options

Unify supports all existing Teams Phone connectivity methods:

• Microsoft Calling Plans: All-in-cloud solution with Microsoft as your carrier
• Direct Routing: Connect certified Session Border Controllers to maintain carrier relationships
• Operator Connect: Carrier-managed service with simplified administration

Licensing Requirements

The Unify model requires Teams Phone licenses for agents and supervisors, plus an Azure Communication Services resource assignment. 

However, you leverage your existing Teams Phone infrastructure investment rather than provisioning separate contact center numbers.

Best Use Cases

Choose Unify when you’re:

• Building new contact center capabilities without legacy system constraints
• Adopting a cloud-first strategy across your communication stack
• Prioritizing AI integration with Azure’s machine learning capabilities
• Seeking single-vendor accountability with Microsoft for the entire solution stack

The Extend Model: Hybrid Integration with Teams Client

How It Works

The Extend model keeps your existing PBX infrastructure while delivering a modern Teams-based user experience. 

It uses Microsoft Graph APIs and the Cloud Communications API to bridge your current telephony investment with Teams functionality.

Key components include:

• Teams client platform integration for user interface consistency
• Graph API calling permissions for call control
• Teams Phone system handling all contact center calls
• Optional Azure Calling Bot for enhanced routing capabilities

Technical Architecture Considerations

Extend introduces additional routing complexity through multiple API interactions. Calls must traverse from your existing system through Graph APIs to Teams Phone, then back to the Teams client. 

Important licensing change: Effective June 2025, Microsoft enforces Teams Phone licenses for all Extend contact center implementations and attendant console solutions. This significantly impacts the cost calculation for hybrid deployments.

PSTN Connectivity Integration

Extend typically pairs with Direct Routing configurations, allowing you to maintain your existing carrier relationships while presenting a unified Teams interface. 

Some implementations may also leverage Operator Connect for simplified carrier management.

Development Requirements

Building Extend solutions requires expertise in:

• Microsoft Graph API development with appropriate delegated permissions
• Teams application certification for app store distribution
• PowerShell administration for advanced configurations

Best Use Cases

Choose Extend when you have:

• Significant existing PBX investments that aren’t ready for retirement
• Complex compliance requirements that mandate specific telephony infrastructure
• Gradual migration strategies moving toward full Teams adoption
• Enterprise-scale deployments with mature change management processes
• When you want your agents to reside in Teams and don’t need deep integration with other systems (i.e. CRM, etc.). This keeps complexity low and the call flow simple.

The Connect Model: Lightweight API Integration

How It Works

Connect represents the most straightforward integration path, using Microsoft Graph APIs and Teams client SDKs for basic interoperability.

Your external system maintains primary call control while syncing essential information with Teams for presence and basic call management.

The architecture relies on:

• REST API integrations for data synchronization
• Webhook configurations for real-time updates
• Teams Graph API permissions for presence and basic calling
• External system telephony infrastructure for actual call handling

Technical Simplicity

Connect’s lightweight approach means minimal Microsoft-specific development requirements. 

You’re essentially building API integrations rather than native Teams applications, making it accessible to development teams without deep Microsoft expertise.

Licensing Model

Connect requires only standard Teams licenses rather than the more expensive Teams Phone add-ons. 

Your primary licensing costs remain with your existing telephony system, making this the most cost-effective integration approach for basic requirements.

Integration Capabilities

While Connect offers the simplest implementation path, it provides limited functionality:

• Basic call control within Teams interface
• Presence synchronization between systems
• Simple click-to-dial functionality
• Minimal reporting integration capabilities

Best Use Cases

Connect works well for:

• CRM system integrations requiring basic Teams connectivity
• Custom applications needing lightweight Teams presence
• Niche workflow requirements without full contact center needs
• Budget-conscious implementations prioritizing simplicity over features
• When the agent needs to live within the contact center and only utilizes Teams for presence. 

Example: This would be like when the organization uses Teams for their phone system but the contact center agents never need the phone system (think like Comcast support, they only use the contact center, never the internal phone system).

Unify vs Extend vs Connect: Technical Requirements Comparison

Decision Framework: Choosing Your Extensibility Model

Infrastructure Assessment

Choose Unify if:

• You’re committed to cloud-first infrastructure strategies
• Legacy system dependencies don’t constrain your deployment timeline
• AI-powered customer experience features align with your roadmap priorities
• Single-vendor support relationships match your operational preferences

Choose Extend if:

• Existing PBX investments require protection during transition periods
• Compliance or regulatory requirements mandate specific telephony infrastructure
• Your organization operates complex, multi-site deployments requiring gradual migration
• Advanced call routing and monitoring capabilities are business-critical

Choose Connect if:

• Integration requirements focus on basic interoperability rather than full replacement
• Development resources or expertise for Microsoft-specific platforms are limited
• Budget constraints prioritize minimal upfront investment over advanced features
• Your primary use case involves custom applications rather than contact center operations

Cost Considerations

The licensing landscape significantly impacts model selection:

• Unify: Teams Phone licenses plus ACS resource costs, but leverages existing telephony investment
• Extend: Teams Phone licenses plus existing system maintenance
• Connect: Standard Teams licenses plus external system costs

Technical Capability Requirements

Each model demands different development skills and architectural expertise:

Unify Development Stack:

• Azure Communication Services SDK proficiency
• Azure AI Services integration experience
• Cloud-native application architecture skills
• Microsoft certification process navigation

Extend Development Stack:

• Microsoft Graph API development expertise
• Teams application platform knowledge
• PowerShell automation capabilities
• Hybrid infrastructure management skills

Connect Development Stack:

• REST API integration experience
• Webhook implementation capabilities
• Basic Microsoft Graph API familiarity
• Minimal Microsoft-specific requirements

Implementation Planning and Next Steps

Getting Started with Your Chosen Model

For Unify implementations:

1. Establish Azure Communication Services resource with Teams Phone extensibility assignment
2. Configure Teams Phone licensing for contact center agents and supervisors
3. Select PSTN connectivity method (Calling Plans, Direct Routing, or Operator Connect)
4. Begin ISV certification process if developing commercial solutions

For Extend implementations:

1. Audit existing PBX infrastructure and integration requirements
2. Plan Teams Phone licensing deployment ahead of June 2025 enforcement
3. Configure Microsoft Graph API permissions for calling and presence access
4. Design hybrid call routing architecture between systems

For Connect implementations:

1. Map integration requirements to available Graph API capabilities
2. Design webhook architecture for real-time data synchronization
3. Configure basic Graph API permissions for Teams access
4. Plan user experience workflows across both systems

Working with Implementation Partners

Given the technical complexity and strategic implications of these decisions, engaging with Microsoft-certified partners often accelerates successful deployments. 

Look for partners with:

• Demonstrated experience in your chosen extensibility model
• Microsoft certifications relevant to Teams Phone and Azure Communication Services
• Industry-specific expertise matching your business requirements
• Proven track record with similar-scale implementations

The Strategic Implications of Your Choice

Your Teams Phone extensibility model choice extends far beyond technical implementation—it defines your organization’s communication strategy for the next several years. 

The key is aligning your choice with both your current constraints and your future ambitions. Microsoft’s extensibility models provide the flexibility to meet organizations where they are today while offering clear paths forward as business needs evolve.

Ready to move forward? Start by conducting an honest assessment of your current infrastructure, future requirements, and organizational capabilities. 

The right choice becomes clear when you match Microsoft’s extensibility models to your specific business context rather than trying to fit your requirements into Microsoft’s preferred approach.

Need help with your Teams Phone options?

That’s where the good folks at Cloud Revolution come in. We don’t like to call ourselves the Teams experts, but we do like to call ourselves the Teams people.

We’re people like Adam Ball, co-founder of the community event, Comms vNext, and Chad McGreanor, who has over 20 years of experience in Microsoft-focused senior roles spanning practice management, consulting, and managed services.

When you opt for Cloud Revolution, you benefit from:

• Microsoft Partner of the Year 2023, Finalist 2022 & 2024
• Proven track record of delivering measurable business outcomes
• Trusted by leading organizations across industries
• Human-centered, relationship-driven approach

Ready to start planning your Teams Phone migration?

Book a call with our Teams Phone people here.