Avoid a rollercoaster Teams Voice migration: Lessons from Merlin Entertainments

Rollercoasters are great for thrill seekers. Not for enterprise voice migrations. 
 
Case in point: Merlin Entertainments, whose voice environment spanned 135 locations across the globe with hotels, resorts, attractions, and offices. The infrastructure mix included analog lines, on-site PBXs, Skype for Business, and thousands of handsets in every shape and standard imaginable. 

A shift to Microsoft Teams Phone could have meant long delays, user disruption, or worse - breaking core services like security phones or contact center flows. 

But that didn’t happen. Instead, Merlin executed a pragmatic, scalable, and flexible migration with a smart strategy and repeatable steps.  
 
Pure IP supported Merlin throughout this transformation. These are the takeaways that helped keep things steady, even when the landscape wasn’t. 

What Merlin did right

• Deployed Microsoft Teams Phone across 135+ sites globally
• Used SIP trunking as a consistent backbone from day one
• Integrated legacy analog and SIP devices without replacing them
• Simplified number porting using automation and a central portal
• Transitioned from in-house SBCs to hosted Direct Routing
• Supported hybrid models for hotels, offices, and field sites
• Reduced operational overhead and centralized telephony management 

1. Don’t treat every site the same

Merlin’s environment was anything but uniform. 

Some locations had: 

• Five phones and one DSL line
• An old analog PBX from the 1980s
• Zero onsite IT support

Others had: 

• Hundreds of phones across a large campus
• A mix of analog, SIP, and Teams-native devices
• In-house technical teams with experience in Skype or legacy voice 

Instead of forcing a single template, Merlin built playbooks based on site type, infrastructure maturity, and operational importance. Some migrated in one go. Others followed phased timelines based on risk or staffing. 

Key considerations they used to plan site-level migrations: 

• Device types and age
• Physical access to endpoints
• Network readiness for cloud voice
• Role of voice in local operations (e.g. guest services vs. back office)
• Onsite IT capability
• Porting feasibility by country
  

Takeaway: Migrations fail when you ignore context. Flexibility wins. 

Our Teams Phone Migration Guide gives you the essentials: what to know, what to map, and how to avoid downtime across mixed estates.

2. Start early with SIP and stick with what works

Merlin started their project before Operator Connect was launched. They built global SIP trunking into their infrastructure from the start. That decision paid off in speed, consistency, and control. 

Their SIP foundation enabled: 

• Consistent DDI handling across regions
• Direct SIP connections to legacy PBXs and contact center platforms
• Seamless number routing during staged migrations
• Early adoption of Direct Routing into Microsoft Teams
• Simplified voice architecture with fewer vendors and interop issues 

Rather than juggling local carriers or dealing with telco delays, they partnered with Pure IP as their provider who could deliver global SIP coverage, fast provisioning, and solid porting support. 

SIP trunking also enabled: 

• Quick onboarding of new sites
• Flexible routing logic by region, user group, or platform
• Easy fallback strategies for contact centers and legacy systems 

Takeaway: SIP isn’t just a transport method, it’s a long-term strategy. The earlier you start, the smoother every future migration becomes. 

Go behind the scenes with Paul Cornish as he unpacks Merlin’s global Teams Phone migration.

3. Build porting muscle, then automate it

Porting is often the riskiest part of any voice migration. At scale, it’s also the most misunderstood. 

Merlin took a measured approach: 

• Started with small batches to build confidence
• Used a centralized portal to manage all porting actions
• Automated bulk migrations where possible
• Worked with a provider experienced in local porting laws across multiple regions
• Built internal knowledge to troubleshoot edge cases and exceptions 

At Pure IP, we adopt a unique approach to number porting which we take our enterprise customers, including Merlin, through.  We support porting in over 50 countries through a single, coordinated process, backed by dedicated project teams, platform integrations, and automation. Customers get migration trunks to separate porting from go-live, pre-port testing to catch issues early, and zero-touch provisioning into Microsoft Teams. The result is a process that’s predictable, repeatable, and built to scale. 

This approach turns number porting from stressor into a strength. 

Instead of treating number moves like one-off projects, Merlin integrated porting into the daily rhythm of operations. It became: 

• Predictable
• Trackable
• Low-touch
• Repeatable 

Porting success factors: 

• Clear escalation paths for local telco delays
• Visibility across in-flight requests
• Support for full and partial porting by site
• Minimal service disruption during cutover 

Takeaway: Build trust in your porting process and scale it like a product. 

4. Legacy devices? Embrace the weird

In an ideal world, you’d start fresh with Teams-certified phones and cloud-native devices. That wasn’t Merlin’s world. 

Instead, they supported: 

• Analog door entry systems
• VVX phones that couldn’t be physically reset
• Paging systems in public areas
• Phones mounted in remote or inaccessible locations
• Hotels still running traditional PBX systems
• SIP handsets that weren’t Teams-native 

Merlin extended device lifespan and avoided expensive replacements by: 

• Using Microsoft’s SIP Gateway for supported SIP devices
• Leveraging analog gateways and ATAs for basic phones and intercoms
• Scripting PowerShell automations to remotely repoint and reconfigure VVX phones
• Running hybrid environments where Teams coexisted with legacy PBXs
• Routing traffic smartly across Direct Routing and internal SBCs 

They built an ecosystem that respected the real world — not just the Teams admin center. 

Takeaway: You don’t need a perfect estate to move forward. Work with what you have. Choose partners that embrace complexity. 

Related: 5 personas you need to plan for in your Teams Phone deployment

5. Offload infrastructure - when it’s time

Merlin once managed over 25 Ribbon gateways across global data centers. It worked — until it became an operational drag. 

As Teams Phone matured, and the SIP trunking strategy solidified, they shifted from in-house SBCs to hosted Direct Routing through Pure IP. The transition gave them: 

• Simplified support
• Less patching, monitoring, and vendor management
• Quicker time to deploy new sites
• Fewer regional limitations on number assignment or routing
• A single point of control for voice infrastructure 

This wasn’t a rip-and-replace. It was a strategic transfer of responsibility. 

Takeaway: The goal isn’t cloud for cloud’s sake — it’s control and scale without the weight of hardware. 

Final thoughts 

Merlin’s journey wasn’t flashy. It was smart. 

They didn’t try to reinvent voice. They worked with the mess — the analog lines, the old handsets, the regional quirks — and used smart strategy and solid tech to make it all run through Teams. 

They chose tools that adapted to their infrastructure. Partners that delivered. And plans that scaled without chaos. 

When the stakes are high and the systems are old, skip the thrill ride. Plan, test, and migrate with confidence. 

FAQs: Microsoft Teams Phone Migrations 

Q: Can Pure IP help with legacy or analog devices during a Teams Phone migration? 

Yes. Our SIP Connect service bridges analog and SIP registered devices — such as fax machines, entry systems, DECT phones, and video conferencing units — into your cloud telephony environment. SIP Connect creates a secure SIP endpoint per device, unified under our global voice platform. You keep using existing hardware while consolidating management and routing into Microsoft Teams.

Learn about SIP Connect.

Q: How should I structure a phased migration to Teams Phone? 

Use a hybrid model: 

• Begin by implementing Direct Routing
• Port DDIs in small batches by site or department
• Use coexistence strategies for call routing between legacy and Teams users
• Phase out legacy systems only after validation

Q: What should I look for in a voice provider for Teams Phone?

• Global number provisioning
• Automated porting tools
• Direct Routing and Operator Connect experience
• Analog and legacy system integration
• Flexible routing and TLS support
  

Q: Can I integrate contact centers with Microsoft Teams Phone?

Yes. Use Direct SIP connections from your Teams SBC to cloud contact centers like NICE or Genesys. This allows you to switch numbers between Teams and contact center platforms without re-provisioning. 

Pure IP can integrate with most industry-leading contact centers.

Q: What are the risks in porting phone numbers during a migration?

• Downtime if porting fails
• Mismatched DDI assignments
• Delays due to local regulations
• Loss of critical services if fallback isn’t available

Mitigate this by: 

• Using a provider with international porting experience
• Running tests before each port
• Staggering migrations across lower-risk time windows
  

Q: How do I manage a mixed environment of Teams, SIP, and legacy PBX? 

Use SIP trunking and Direct Routing to bridge all platforms. You can: 

• Route calls between Teams and on-prem systems
• Maintain analog support via gateways
• Port numbers gradually
• Manage routing logic centrally 

This lets you phase migration without disrupting core services. 
 

Q: Should I use Operator Connect or Direct Routing for Teams Phone?

It depends on how much control, flexibility, and integration you need. 

Use Operator Connect if you want: 

• A faster, more native Microsoft onboarding experience
• Less infrastructure to manage
• Basic call plans without complex routing 

Use Direct Routing if you need: 

• Support for legacy systems or analog devices
• Custom call flows or advanced compliance requirements
• Integration with third-party platforms like contact centers or PBXs
• Global PSTN coverage beyond Microsoft’s in-region footprint