Email us at sales@ocgl.net
Email us at sales@ocgl.net
Blog
27Aug 2026
A Teams Phone migration rarely fails because the technology does not work. It fails because something nobody inventoried turns out to matter: an elevator phone, a fax line, a main number that took three weeks to port, or a network that had never carried a voice call before.
This post closes our four-part series for owners and leadership teams. Part 1 made the case for one platform, Part 2 covered meeting rooms and Copilot, and Part 3 explained Teams Phone and how to get dial tone. Here we set the stage for the migration itself, and for the deeper series that follows.
Phone systems are unusual. Nobody notices a good one, and everybody notices a bad one within about four minutes. A file migration that goes sideways is embarrassing, but a phone migration that goes sideways means clients cannot reach you.
Consequently, the work happens before the cutover, not during it. Below are the five areas that decide whether a migration is uneventful.
Start with numbers, then go looking for the ones that are not on anyone’s list. Almost every business has more telephony than it thinks.
That analog list is the single biggest trap. Microsoft’s supported path for these devices is an analog adapter behind a certified session border controller using Direct Routing. Notably, SIP Gateway explicitly does not cover analog phones, fax or paging. Your options are to add Direct Routing alongside a calling plan in the same tenant, keep a small analog service for those circuits, or replace the devices. Elevator and fire lines usually carry inspection obligations of their own, so confirm those with the building owner and the inspecting authority rather than assuming.
Voice is the least forgiving traffic on your network. Fortunately, Microsoft publishes exactly what it needs.
Budget around 100 Kbps symmetric per concurrent call, and size for peak concurrency rather than headcount. Then configure quality of service properly. Microsoft assigns audio to client source ports 50,000 to 50,019 and expects DSCP 46, Expedited Forwarding. Marking at the router and in the client together is the reliable approach, and QoS must also be enabled globally in the Teams admin centre.
Three more items matter more than they sound:
Microsoft’s Network Planner and Advisor for Teams will do much of the assessment for you, and the Call Quality Dashboard becomes your evidence after go-live.
Porting is where optimistic timelines meet carrier reality. Canada requires a minimum 10-day lead time, compared with five days in the United States, and the losing carrier has five to seven business days to respond. Microsoft advises that a port order typically takes 7 to 14 days end to end, and up to 30 days with some providers. Orders above 200 numbers take longer still.
Most rejections are avoidable. In Microsoft’s own words, mismatched account information is the most common cause of errors and delays. Therefore, before you submit anything:
One sequencing detail saves real pain: assign calling plan licences and emergency locations before the port completes, not after.
Emergency calling is not a checkbox at the end. It is a small project of its own, and it has to be finished before anyone relies on the new system.
The sequence runs like this. Create and validate emergency addresses for every site with geographic coordinates, assign a registered address to every user and number, define your trusted external IP addresses, define network sites and subnets, then populate the location information service for subnets, switches, ports and access points. Teams matches those in a set order: access point, then switch port, then switch, then subnet.
After that, test with 933 from every site. Also plan around the known gaps, because the web client does not support dynamic emergency calling, Teams desk phones cannot use Wi-Fi identifiers for location, cloud proxies that rewrite source addresses break detection, and network changes can take up to four hours to propagate.
Not everyone needs a desk phone, and that is usually the first budget conversation. Certified hardware comes from Yealink, Poly, AudioCodes and Crestron. If you already own SIP phones, SIP Gateway may let you keep them signed in with corporate credentials, subject to the analog exclusions noted above.
For the cutover itself, Microsoft sanctions the approach that reduces risk most: mix connectivity options in one tenant. You can run calling plans as the base, add Teams Phone Mobile for field staff, and keep Direct Routing for the analog estate. That is what makes a phased migration possible rather than a single nervous weekend.
Use device update rings so a small validation group takes firmware first. Pilot with one department that has real external call volume, not with the IT team. Keep unassigned number routing configured so no orphaned number ever rings out to nothing. Finally, train people on voicemail, transfer and call queues a week before their number moves, not on the day.
A clean Teams Phone migration is mostly discovery and sequencing. Find the analog devices early, get QoS and the network right, start porting conversations weeks before you want the numbers, treat emergency calling as a deliverable, and phase the cutover rather than flipping a switch.
Get those five right and the migration itself is quiet. That is the whole objective.
This post sets the stage. Over the coming weeks we will go deeper on each stage of a Teams Phone migration, including a full discovery checklist, a network readiness assessment you can run yourself, the porting playbook step by step, emergency calling configuration in a Canadian context, and choosing the right devices for each type of user.
First, though, there is homework. Our free Teams Phone migration checklist lists exactly what to gather before anyone writes a statement of work, from six months of invoices to the switch ports behind your desk phones.
Thinking about moving off an aging phone system, or partway through planning and unsure what you have missed? OPUS Consulting Group runs Teams Phone migrations for organizations across Metro Vancouver and Canada, coast to coast, especially those with 15 to 70 people. Explore our Microsoft Integration, IT Consulting and Managed IT Solutions services, or start a plain-language conversation: sales@ocgl.net • 1-866-800-OPUS (6787) • visit www.ocgl.net. Start the series from the beginning with Part 1 on the Microsoft Teams collaboration platform.
1-866-800-OPUS (6787)