How to Choose a Microsoft Teams Voice Migration Partner: Four Criteria Most RFPs Miss

TL;DR

• A good migration partner looks at everything on your phone system, including SMS, fax, contact center, call recording, analytics, and paging, and recommends the connectivity model that fits your business.
• Software-led discovery gives you a verified inventory of every number, device, and dial plan rule. Interviews and spreadsheets give you what people remember.
• Ask who runs your Teams Phone environment after cutover. A strong partner stays, and gives your help desk a safe way to make everyday changes without PowerShell or admin roles.
• Ask who pays when discovery finds something nobody counted. It almost always does.

Most enterprises shortlist a Microsoft Teams voice migration partner the way they buy software: demos, references, price. That process rewards the best presentation, which tells you little about how the migration will go.

Four things decide whether the project lands: how the partner discovers what's actually in your environment, how they choose a connectivity model, who runs the system after cutover, and who pays when discovery finds something nobody counted.

Most RFPs don't test for any of them. You can, in your first call with each vendor.

Why Teams voice migrations stall

Migrations rarely fail at cutover. That's just where it shows up. They fail in the six months before, when nobody mapped the real environment, and in the six months after, when the partner has moved on.

A dial plan that looked correct on paper sends calls to the wrong queue, because a hunt group rule hasn't been touched since a 2017 acquisition. An overhead paging system goes silent the day CUCM is switched off, because nobody knew what was plugged into the analog gateway feeding it.

Real discovery covers everything on your phone system: SMS, fax, contact center, call recording, analytics, paging. If you don't know what you have, you can't design what comes next.

Criterion 1: How does the partner discover what's actually in your environment?

Interviews and spreadsheets cost you twice. The scope rests on assumptions, and gathering them takes time your business stakeholders don't have.

Software-led discovery reads the system directly. It returns a verified inventory: every DID, every analog port, every call queue, every dial plan rule, every device, including the ones nobody remembers. That gap is widest in Cisco CUCM, Avaya and Mitel environments built up through mergers and site additions.

Copying old settings into Teams carries old mistakes with them. A good partner shows you a better design while they have the map in front of them.

Microsoft FastTrack gives you Microsoft's guidance on Teams Phone. It doesn't send people to discover and move your phone system. A vendor who treats it as a migration resource hasn't done this work before.

Ask in the first call:

• "What tool do you use to discover our environment?" A vendor who answers with interviews and spreadsheets is telling you the scope will rest on assumptions.
• "Can you show us a sample discovery output before we sign?" A real sample has device counts, dial plan maps, and number inventories. A vendor who hedges doesn't have one.

Criterion 2: How does the partner choose your connectivity model?

This is where you find out whether a partner is advising you or selling to you. Many partners are certified with one or two carriers and recommend the model that pays them. A good partner asks about your carrier contracts, analog devices, international sites, and contact center first, and recommends after that.

There are three ways to connect Teams Phone to the phone network. Microsoft Calling Plans are the simplest: Microsoft is your carrier, in the countries it covers. Operator Connect lets a certified carrier plug straight into Teams with no Session Border Controller to run, and it fits many enterprises well. Direct Routing connects any carrier through a Session Border Controller, which suits existing carrier contracts and locations the other two don't reach. Teams Phone itself carries Microsoft's 99.999% uptime SLA (Microsoft Teams Phone). For a side-by-side comparison, see Direct Routing vs. Operator Connect.

Analog devices don't decide the model on their own. Some paging systems and door phones register directly with Teams Phone. Others need an adapter or gateway. Discovery tells you which kind you have.

Ask in the first call:

• "How do you decide which connectivity model to recommend?" A strong partner asks about your contracts, devices, and sites before answering.
• "Which models have you deployed in the past year?" If the answer is the same model every time, that's their default, and it will be yours too.

Criterion 3: Who owns your Teams Phone environment after go-live?

Many partners measure success at cutover and move on. Your team runs the phone system every day after that, so ask what the partner leaves behind and whether they stay.

What running it after cutover takes:

• A way for a non-specialist to change a call queue or provision a user safely, without PowerShell or powerful Microsoft 365 admin roles
• E911 dispatchable location management across every office address, updated whenever people or sites move
• Monitoring that surfaces a misconfigured setup before a user complains
• One accountable owner for the moment Microsoft and the carrier point at each other

E911 is worth raising early. FCC rules put the duty to keep dispatchable locations current on the business that runs the phone system, not on Microsoft. One Teams-specific limit: Wi-Fi-based locations don't work on Teams desk phones, so map their subnets or switch ports instead. That matters in branch offices still running desk phones.

Ask in the first call:

• "Who owns a problem that sits between you, Microsoft, and our carrier?" A strong answer names a specific escalation path, not a shared inbox.
• "Can a non-specialist on our help desk make everyday changes safely?" A vendor who answers "submit a ticket to us" is describing a queue between your team and every routine move, add, and change.

Criterion 4: Who pays when discovery finds something?

Discovery almost always finds something: forty analog endpoints nobody counted, a site added last year, a contact center nobody mentioned. What matters is whether that changes your price.

Some partners quote low and make it back on change orders. Others pad the quote to cover what they haven't found yet (we will never do that to you). Either way, you want to know before you sign, and the same goes for the go-live date.

Ask in the first call:

• "What happens to the price if discovery finds something nobody counted?" A strong answer is a fixed price that holds, or a change-order process tied to the discovery output.
• "Have you ever billed a customer more than the quote?" Ask for a straight answer.

The first-call test

What these criteria won't tell you

A vendor can answer all four cleanly and still be the wrong partner for your environment. These questions screen out the ones who haven't done this work. They don't pick the winner among the ones who have.

Automated discovery finds everything that's running. It won't tell you what to keep. It sees the analog gateway, not what's plugged into it, so someone still has to walk the building. If your numbering scheme has been accreting exceptions since 2009, somebody on your side still has to decide what survives the move. A good partner puts that decision in front of you in week two, as a design conversation, instead of in week nine, as an outage.

How ZIRO answers the same four questions

We'd want every customer to ask us these questions, so here are our answers. We look at everything that runs on your phone system and recommend what fits, whatever model that turns out to be.

Discovery. The ZIRO Platform scans your phone system before anything is touched: every number, device, call queue, and dial plan rule, including the Call Manager rules nobody on your team can explain anymore. We also ask about everything else that runs on it, from SMS and fax to call recording and the contact center.

Connectivity. We design across Microsoft Calling Plans, Operator Connect, and Direct Routing, including bring your own carrier. We recommend one after we've asked about your contracts, devices, sites, and contact center.

After cutover. We stay. The ZIRO Platform lets a tier-one tech make safe moves, adds, and changes without PowerShell and without calling a specialist. Copeland runs 75 locations this way. Ekin Gümüş, Global Service Lead, Enterprise Voice Operations & Engineering: "ZIRO is the best product for managing Teams Phone. It solved provisioning for me, and I can't put a price tag on the time I've saved."

Pricing. Every ZIRO engagement is fixed fee. The price we quote is the price you pay. The University of New Haven moved 1,000+ users off Cisco Call Manager in phases over six months. Greg Bartholomew, IT Director: "ZIRO didn't just sell us a solution, they became an extension of our team."

A migration is also the best time to decide whether an AI agent should answer some of your calls. We cover that in Six jobs a Teams Phone Agent can take off your plate.

Frequently Asked Questions

What does Microsoft FastTrack cover for Teams Phone migration?

FastTrack gives you Microsoft's guidance and best practices for Teams, including voice. It doesn't do the migration work itself: discovering your current phone system, designing PSTN connectivity, and moving your numbers. Plan for a partner or your own team to do that part.

What's the difference between Operator Connect and Direct Routing?

Operator Connect uses a certified carrier that has built its integration with Microsoft. It's simpler to set up, there's no SBC to manage, and it fits many enterprises well. You're limited to that carrier's coverage. Direct Routing uses a Session Border Controller to connect any carrier, lets you keep an existing carrier contract, and works in countries Microsoft Calling Plans doesn't reach.

How long does a Microsoft Teams voice migration take?

It depends on how complex your environment is, how many sites you have, and the pace you set. The University of New Haven moved 1,000+ users off Cisco Call Manager in phases over six months, a pace chosen for adoption. A vendor who quotes a go-live date before discovery is guessing.

What happens to analog devices and overhead paging during a migration?

It depends on the device. Some paging and door phone manufacturers make devices that register directly with Teams Phone, with no SBC required. Others need an Analog Telephone Adapter or a gateway. Discovery is how you find out which kind you have. A partner who recommends Direct Routing before looking at your devices is guessing.