Senior Voice Engineer

The Opportunity We are looking for a technically strong, hands-on Voice Engineer to lead the end-to-end migration of an existing Avaya telephony environment to Microsoft Teams Phone. This is a hands-on engineering and delivery role, not simply an advisory or architectural position. You will take ownership of the technical discovery, solution design, implementation, migration and transition into operational support. The ideal candidate will have personally implemented Avaya telephony solutions and successfully delivered migrations to Microsoft Teams Phone, including complex enterprise environments with legacy integrations. You will work closely with Microsoft 365 specialists, network engineers, service desk teams, telecommunications carriers and key business stakeholders. Responsibilties include:

1. Discovery and Technical Assessment

• Conduct detailed audits of existing Avaya telephony environments including users, extensions, DDI ranges, hunt groups, call routing, voicemail and SIP trunks.
• Identify existing integrations such as call recording, analogue devices, contact centres and legacy telephony services.
• Assess network readiness, bandwidth, QoS, firewall configurations and Microsoft Teams licensing requirements.

2. Solution Architecture and Design

• Develop high-level and low-level designs for Microsoft Teams Phone solutions.
• Design PSTN connectivity using Direct Routing, Operator Connect or Microsoft Calling Plans.
• Define dial plans, voice routing policies, call queues, auto attendants and emergency calling configurations.
• Design SBC architecture, service resilience and business continuity requirements.

3. Hands-on Engineering and Implementation

• Configure and deploy Microsoft Teams Phone environments.
• Implement and manage Session Border Controllers including AudioCodes or Ribbon.
• Establish SIP connectivity and interoperability between Avaya and Microsoft Teams during migration.
• Configure call routing, numbering plans, policies and voice services.
• Automate bulk user provisioning and administration using PowerShell.

4. Migration Delivery

• Develop and execute phased migration strategies across sites, departments and user groups.
• Coordinate UK telephone number porting and telecommunications carrier activities.
• Manage pilot migrations, technical testing, production cutovers and rollback procedures.
• Resolve technical challenges involving legacy telephony integrations and business-critical services.
• Ensure minimal disruption to users and business operations.

5. Operational Transition and Support

• Support business adoption through stakeholder communications and technical knowledge transfer.
• Troubleshoot SIP, RTP, call quality and connectivity issues.
• Monitor and optimise service performance using Microsoft Teams Call Quality Dashboard and associated tools.
• Produce technical documentation, operational runbooks and support handover materials.
• Support the controlled decommissioning of legacy Avaya infrastructure and redundant telecommunications services. Essential skills required are We are looking for candidates who can demonstrate:
• 5+ years of enterprise voice engineering experience.
• 3+ years of hands-on Avaya Aura experience, including Communication Manager, Session Manager and System Manager.
• At least two successfully completed migrations from traditional PBX platforms to Microsoft Teams Phone, including at least one Avaya migration.
• Proven experience as a lead or principal technical engineer responsible for telephony migration delivery.
• Strong Microsoft Teams Phone implementation experience covering Direct Routing, Operator Connect, call queues, auto attendants and voice routing.
• Practical experience configuring SBCs, preferably AudioCodes or Ribbon.
• Advanced knowledge of SIP, RTP, SRTP, SIP trunking and enterprise voice networking.
• Experience managing coexistence between legacy Avaya systems and Microsoft Teams.
• Understanding of UK telephone number porting, PSTN connectivity and ISDN-to-SIP migrations.
• Strong PowerShell scripting skills for Microsoft Teams voice administration.
• Experience with Microsoft 365, Entra ID and Teams administration.
• Knowledge of network technologies including VLANs, QoS, firewalls, NAT and real-time media optimisation.
• Ability to diagnose complex voice issues using Wireshark, SBC logs and call tracing tools.
• Strong technical documentation, stakeholder communication and problem-solving capabilities. Technical specification Candidates should have practical knowledge across several of the following technologies: Avaya Technologies
• Avaya Aura Communication Manager
• Avaya Session Manager and System Manager
• Avaya SBCE
• Avaya G430/G450 Media Gateways
• Avaya IP Office
• Avaya Messaging and call routing Microsoft Technologies
• Microsoft Teams Phone
• Direct Routing and Operator Connect
• Microsoft Teams Admin Centre
• Microsoft Entra ID
• Microsoft Teams PowerShell
• Teams Call Quality Dashboard
• Microsoft 365 licensing and administration Voice and Networking
• AudioCodes Mediant and Ribbon SBC
• SIP, RTP, SRTP and TLS
• PSTN and SIP trunking
• QoS, DSCP, VLANs and network routing
• E.164 numbering and dial plans
• Wireshark and SIP troubleshooting Ideal certifications required Essential
• Microsoft 365 Certified: Collaboration Communications Systems Engineer Associate (MS-721 or predecessor MS-720).
• Microsoft 365 Certified: Teams Administrator Associate (MS-700). Highly Desirable
• Avaya Aura certification (ACIS, ACSS or ASTA).
• AudioCodes or Ribbon SBC certification.
• SIP School Certified Associate (SSCA).
• Cisco CCNA or CCNP Collaboration.
• ITIL 4 Foundation. We recognise that vendor certifications evolve. Relevant legacy or expired Avaya certifications will be considered where supported by recent practical implementation experience. Demonstrable hands-on delivery experience is particularly important.