Microsoft Teams Voice Migrations & Solutions

Microsoft Teams Voice Migrations & Solutions

Make Microsoft Teams your enterprise phone system

Microsoft Teams is already where your people work, but for most organisations it still isn’t the phone system.

Teams can replace legacy telephony in full, but only when it’s engineered as an enterprise voice platform, not switched on as a feature.

FourNet delivers large-scale Teams Voice with resilient Direct Routing, structured migration governance and compliant recording built in - from PSTN replacement to 20,000+ number migrations. Delivered on the same secure foundation as your wider estate: network, security and voice under one accountable partner.

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When Teams Becomes Your Telephony Platform

Teams Voice succeeds when it is architected as a controlled voice platform, not deployed as an afterthought.

Microsoft Teams now has more than 320 million users worldwide, yet only a fraction use it for full external (PSTN) calling. Most organisations have Teams for collaboration but still run telephony somewhere else, on legacy PBXs and parallel SIP contracts. The PSTN switch-off changes that: from 31 January 2027 the old copper network is gone, and every legacy line has to move to IP before then. The opportunity is real - one platform for collaboration and calling, under one security and identity model - but replacing telephony across hundreds of sites or tens of thousands of numbers carries risk if it’s rushed: disruption during porting, inconsistent experience, weak compliance controls, limited resilience.

How FourNet Makes Teams a Genuine Enterprise Voice Platform

  • Resilient Direct Routing Architecture

    We implement structured Direct Routing with geographic diversity and failover pathways. SIP connectivity is governed, monitored and aligned to your availability requirements. Voice is engineered for continuity, not convenience.

    This architecture ensures Teams operates as an enterprise telephony platform – not simply a collaboration overlay.

  • Structured PSTN Replacement & Number Migration

    Number porting is sequenced, documented and risk-assessed. Parallel running strategies and fallback plans reduce operational exposure. Migration velocity is balanced with service continuity.

  • Compliance & Recording Governance

    Where regulatory obligations apply, compliant recording, retention policies and access controls are embedded from day one. Teams becomes audit-ready rather than administratively exposed.

  • Integration Across CX & Collaboration

    Teams Voice integrates directly with contact centre platforms such as CXone. Presence visibility and internal escalation reduce transfer delays and improve resolution times across customer journeys.

Safe, scalable Teams Voice migration - proven in live environments

Teams Voice can replace legacy telephony at scale - but only with structured governance. FourNet delivers controlled migrations across complex estates without disrupting live services.

  • Numbers migrated to Microsoft Teams Voice

    21,000

    University of Manchester - legacy telephony replaced with a resilient, scalable Teams Voice platform.

  • Full telephony cutover

    One weekend

    Surrey County Council - no disruption to live services across a distributed public-sector estate.

Our Migration Methodology

Enterprise telephony migration requires control. Our approach includes the following.

Speak to a Teams Voice specialist

  • Discovery & Baseline

    Audit existing PBXs, SIP estates, number ranges, call flows and compliance obligations.

  • Architecture & Risk Modelling

    Design Direct Routing topology, resilience tiers and recording integration aligned to business continuity requirements.

  • Phased Migration Planning

    Sequence sites and user groups. Define fallback plans and communication strategy. Protect frontline services during transition.

  • Controlled Execution

    Port numbers in governed waves. Monitor performance in real time. Stabilise before progressing.

  • Optimisation & Governance

    Post-migration reporting, adoption tracking and service reviews ensure performance improves over time.

Hosting and Connectivity Options

Teams Voice architecture can integrate with: 

  • FourNet's UC3 SIP platform 
  • Agile Cloud for resilient infrastructure 
  • ANTENNA for government-grade hosting 
  • Public cloud connectivity models 
  • Hybrid environments where on-premise elements remain necessary 

The deployment model is selected based on resilience, sovereignty and commercial requirements. 

Where Teams Voice Fits in the FourNet Portfolio

Teams Voice runs on the same secure foundation as the rest of your estate -- cyber, network and AI under one accountable partner. UC3 can sit underneath it for resilient SIP governance, and CX platforms connect for unified employee and customer communication.

Unified Communications (UC3) Secure Connectivity & Cloud Cybersecurity & Resilience

Modernise Telephony with Confidence

Microsoft Teams can transform enterprise voice - when it is engineered properly. Speak to FourNet about migrating to Teams Voice safely, securely and at scale.

Our Approach

  • Discovery

    Discuss your challenges and goals with us.

  • Analysis

    Thorough examination of your current systems.

  • Roadmap

    Tailored strategy for a secure customer experience.

"FourNet's customer experience consulting has revolutionized our approach. Their team's knowledge and commitment are unmatched."
Elias Thorne, CEO, Innovative Solutions Inc.

If you’re already a client, please call us at 0845 055 6366 or email hi@fournet.co.uk.

What Makes Our Teams Voice Deployment Different

  • Designed for Large Estates

    Our experience includes multi-site councils and universities with tens of thousands of users. 

  • Governance Before Go-Live

    Migration risk, recording compliance and fallback strategies are defined before execution. 

  • Direct Routing as a Resilience Layer

    SIP architecture is engineered for availability rather than treated as a simple connectivity exercise. 

  • Optimisation Beyond Deployment

    Performance reporting, adoption monitoring and structured service reviews embed continuous improvement. 

Frequently Asked Questions

  • Can Teams fully replace our PBX? 

    Yes – when deployed with resilient Direct Routing, structured SIP governance and compliant recording. We design Teams Voice as a full enterprise telephony platform. 

  • How do you minimise disruption during migration? 

    We baseline your estate, sequence porting in controlled waves and implement fallback models where necessary. High-risk services are migrated with additional safeguards. 

  • Do we need UC3 as well? 

    UC3 can provide structured SIP governance and resilience where required, but deployment models are selected based on your architecture and commercial objectives. 

  • How does Teams integrate with contact centres? 

    We integrate Teams presence and escalation into CX platforms such as CXone, allowing agents to collaborate internally without disrupting customer journeys. 

  • What happens after migration? 

    Service reviews, performance monitoring and Customer Success oversight ensure adoption remains strong and optimisation opportunities are identified early.