Telephony migration means replacing or modernizing an end-of-life PBX or IVR without disrupting your operations. Proprietary hardware that is no longer supported, analog, TDM or PRI lines being phased out, expensive licenses, an IVR you cannot change without calling the vendor: the reasons vary, but the risk is always the same. Nobody can afford to drop calls.
Voxivra runs these migrations with a phased approach. Old and new systems coexist, call flows move over one at a time, and every step has a rollback plan.
When to consider a migration
- End of support for your PBX or IVR, or replacement parts that are hard to find.
- Carrier retiring analog, TDM or PRI lines, which forces a move to SIP.
- Locked-down IVR: every menu change requires the vendor, with the delays and costs that come with it.
- Integration needs: CRM connectivity, voicebots or call analytics that the legacy system cannot support.
- Multi-site consolidation: several mismatched PBXs to bring under one architecture.
What we migrate
- Proprietary PBXs to Asterisk or FreePBX, on physical servers, virtual machines or in the cloud.
- Existing IVRs and voice servers, rebuilt as a custom IVR that is easier to evolve.
- Carrier connections to SIP trunks, with number porting.
- In-house voice applications (scripts, older telephony interfaces) to AGI or Asterisk ARI.
- Older Asterisk versions to a maintained release, including the move from chan_sip to PJSIP.
Our zero-downtime migration method
1. Audit the current system
We document everything the current system actually does: numbers, dial plans, business-hour rules, queues, menus, prompts, recordings, integrations, extensions and endpoints. This step often surfaces undocumented rules that teams rely on without realizing it.
2. Design the target architecture
We define the target platform: Asterisk and PJSIP at the core, a SIP proxy (Kamailio or OpenSIPS) for load distribution where needed, redundancy matched to how critical your lines are, TLS/SRTP encryption and toll fraud protection.
3. Run both systems side by side
The new platform is connected to the old one over SIP. Both run in parallel, so a single number, queue or site can be routed to the new platform while everything else stays on the legacy system.
4. Cut over gradually
We start with a low-risk call flow, observe, fix, then expand. Each cutover is scheduled, tested with real calls and backed by a documented rollback procedure.
5. Decommission
Once every flow is migrated and stable, the legacy system is shut down, after confirming what must be archived (recordings, call logs).
We cover the IVR side of this approach in more depth in How to modernize a legacy IVR.
Common migration risks and how we handle them
- Undocumented behavior: a holiday rule, a hidden transfer, a fax line nobody mentioned. The audit and side-by-side period exist precisely to catch these before cutover.
- Number porting delays: carriers set their own timelines, and a rejected port request can push a date back. We start porting paperwork early and never schedule a cutover that depends on an unconfirmed port.
- Network readiness: SIP and RTP are sensitive to firewalls, NAT and bandwidth. We validate the network path, QoS and codecs before moving real traffic.
- Endpoint compatibility: some older desk phones or analog devices cannot register to a modern platform. We list them early and plan replacements or adapters.
- Training and change management: agents and receptionists need to know what changes for them. Short, role-specific guides usually work better than long manuals.
- Security from day one: a new SIP platform exposed to the internet is scanned within hours. Fraud protection and access controls are in place before the first number is moved.
How a project runs
| Phase | Scope | Deliverable |
|---|---|---|
| Audit | technical and functional inventory | map of the current system |
| Design | target architecture, migration plan | architecture document, schedule |
| Build | installation, call flow rebuild, testing | platform in staging |
| Cutover | flow-by-flow migration | cutover sign-offs |
| Stabilization | close monitoring, fixes | operations documentation |
Duration depends on the number of sites, numbers, call flows and integrations, as well as carrier lead times for porting. We provide an estimate after the audit.
What to expect and prerequisites
What you get: an open, documented and maintained platform with no vendor lock-in for every change, ready for automation and voice AI.
Prerequisites:
- administrator access to the legacy system, or at least its configuration exports;
- carrier contracts and contacts so porting can be planned;
- a list of existing integrations (CRM, call recording, monitoring);
- cutover windows agreed with business teams;
- someone who can sign off on each migrated call flow.
For organizations that cannot tolerate any interruption, such as the public sector, we build high-availability requirements into the design and provide extra support during cutover.