Replacing BT One Phone: 12-Step UCaaS Migration Guide UK

With the UK’s PSTN and ISDN switch-off rapidly approaching in 2027, thousands of businesses are actively looking to replace legacy systems like the BT One Phone with modern Unified Communications as a Service (UCaaS) platforms like RingCentral, 8×8, or Microsoft Teams.

However, migrating your entire telephony infrastructure overnight is a high-risk approach. For organizations that require 100% uptime—especially those in legal, financial, or healthcare sectors—a “rip-and-replace” is out of the question.

At Dragonfly Tech, we specialize in phased migrations. Below is the exact 12-step blueprint our engineers use to ensure zero downtime, strict compliance, and seamless user adoption during your transition to the cloud.

Phase 1: Discovery & Audit

Step 1: The Infrastructure & Number Audit

Before any technology changes, we document every existing landline, DDI (Direct Dial Inward), toll-free number, and mobile connection currently tied to your legacy PBX system.

Step 2: Network Readiness Assessment

A cloud phone system relies on your internet connection. We audit your current broadband or leased line to ensure sufficient bandwidth, minimal latency, and proper QoS (Quality of Service) to prevent dropped calls.

Step 3: Feature Mapping

What features keep your business running? We map out your existing Call Queues, IVRs (Auto-attendants), voicemail-to-email, and call recording requirements to ensure they are replicated—and improved—on the new platform.

Phase 2: Design & Strategy

Step 4: Platform Selection

Based on the audit, we match your business with the exact platform (Microsoft Teams Phone, RingCentral, 8×8, or Mitel) and license types needed to suit your hybrid workforce.

Step 5: The Number Porting Agreement

We initiate the UK porting process with Ofcom-regulated timelines to transfer your existing business numbers to the cloud without losing a single digit.

Step 6: Hardware & Endpoint Strategy

We help you decide which users need physical VoIP desk phones, which require high-quality wireless headsets, and who will rely solely on the mobile or desktop softphone app.

Planning your migration? Keep this guide handy.

Download our complete 12-Step UCaaS Migration Checklist to share with your team.

REQUEST YOUR FREE MIGRATION CHECKLIST

Phase 3: Configuration & Integration

Step 7: Call Routing & IVR Build

We pre-build your call flows in the cloud before anything goes live. This includes setting up out-of-hours routing, holiday schedules, and department hunt groups.

Step 8: CRM & Software Integration

We connect your new UCaaS platform to your existing tech stack (Salesforce, HubSpot, Microsoft 365, Zoho) to enable “click-to-dial” and automated customer data pop-ups.

Step 9: Compliance & Recording Setup

For legal and financial teams, we activate and configure encrypted call recording and archiving to meet FCA, SRA, and MiFID II compliance standards.

Phase 4: The Phased Rollout

Step 10: Pilot Testing (The Sandbox)

Before turning off the old system, we roll out the new platform to a small “champion” group (e.g., the IT team or a single branch) to test call quality and routing in the real world.

Step 11: End-User Training

We provide hands-on training for your staff to ensure they know how to use the “Call Flip” features, mobile apps, and video conferencing tools to maximize adoption.

Step 12: The Phased Cut-Over & Support

We execute the migration department by department. The old system is only turned off once the new system is verified as 100% operational. Finally, Dragonfly provides post-launch “hyper-care” support to resolve any immediate user queries.

Ready to secure your business communications?

A successful migration is about more than just software; it is about having a trusted UK partner to guide you through the transition. If your business is preparing to move away from a legacy system, let’s talk.

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Simon Stratton

Simon leads Dragonfly’s technical team, helping UK SMEs slash carbon footprints, printing costs, and telecoms expenses through smart Managed Print and Telecoms Services. He regularly shares insights on document security, cloud integration, and connected business solutions.”