MSP Onboarding Checklist: Move Customers onto Hosted PBX

Tom Reed · Updated 27 October 2026

Onboarding a customer onto hosted PBX goes smoothly when you run the same runbook every time. Capture users, numbers, opening hours and call routes first, then set up the customer's phone system, connect their SIP trunk, build and test call flows, and roll out the apps by email invite before a planned cutover day. Finish with a handover pack, so the customer knows who to call when something changes.

This guide is for MSPs, ITSPs, VoIP providers and IT resellers onboarding business customers onto a hosted phone system they resell. It's a voice runbook, not a general IT client onboarding checklist. Where we mention SessionPBX, Teams Phone and Teams Business are SessionPBX plans, not Microsoft Teams.

What should an MSP onboarding checklist for hosted PBX cover?

A good MSP onboarding checklist covers eight stages, in the same order for every customer: discovery, customer setup, trunk and numbers, call flows, apps and users, trial to paid, cutover and handover. Each stage has an owner and a clear "done when" test. Running them in order turns every customer migration into a repeatable job.

The order matters. Setup needs discovery, call flows need the trunk and users in place, and apps go out once routes are ready. The move from trial to a paid subscription runs alongside the technical work, so it never becomes a last-minute surprise.

If you're still weighing whether voice belongs in your service catalogue at all, start with our guide on whether your MSP should add hosted PBX. Copy the checklist below for each new customer and tick it off as you go.

MSP onboarding checklist for hosted PBX

Discovery

• Users, extensions and who answers which calls, captured in one sheet.
• Existing numbers, current carrier, opening hours, holidays and the devices each person uses.

Customer setup

• Customer project created under your partner account.
• Hosting region chosen and recorded for the customer.

Trunk and numbers

• Customer's SIP trunk connected and registered.
• Number move booked with the losing and gaining carriers, if numbers are changing carrier.

Call flows

• Menus, schedules, announcements and ringing destinations built as a draft.
• Every route walked through with the customer, then published.

Apps and users

• Every user invited by email.
• Every user signed in on at least one device.

Trial to paid

• Trial status and end date noted against the customer.
• Subscription purchase planned and owned by a named partner administrator.

Cutover

• Cutover-day checklist completed and signed off.

Handover

• Handover pack sent and the customer's main contact briefed.

What do you need to find out in discovery?

Every question you skip in discovery becomes a ticket after go-live. Leave with one sheet that anyone on your team could build the phone system from.

Capture these areas:

• Users and extensions. Who needs a phone line, what their extension should be and whether anyone shares a role. A clear phone extension numbering plan saves renumbering later, so agree the scheme before you create accounts.
• Existing numbers and carrier. Every number the customer publishes, which carrier holds each one today and whether those numbers are staying with that carrier or moving to a new one.
• Opening hours and holidays. Normal hours for each day, lunch cover, seasonal closures and what callers should hear when nobody is in.
• Who answers what. Which calls go to reception, which go straight to a team and which go to one named person. This is the raw material for your call flows.
• Groups and queues. People who should ring together, ring in turn or wait in a queue for the next free colleague.
• Voicemail. Who needs a personal or shared mailbox, and who checks it.
• Devices. Whether each person works at a computer, on a mobile or both.

Use the customer's own words for teams and roles, and note anything unusual, such as a number printed on vans. Finally, agree who signs off call flows and who is your contact on cutover day.

How do you set up the customer's phone system?

Set up one phone system per customer, kept separate from every other customer, so a change for one can't spill into another.

On SessionPBX, each customer gets their own SessionPBX project under your partner account. You create it, you own it, and you manage extensions, numbers, the SIP trunk and call flows for that customer. Our guide to multi-tenant PBX for MSPs explains how this model works.

Next, choose where the customer is hosted. SessionPBX lets you choose where each customer is hosted: the UK (London), the US (New York) or Singapore. Each region has its own database. Pick the region closest to the customer's team and check any rules about where their data is kept. Our guide to phone system data residency covers the questions to ask.

Then choose the plan. Teams Business adds ring groups, call queues, visual call flows with IVR and business hours, recording, supervision tools and logo branding. If discovery showed menus, queues or out-of-hours routing, choose Teams Business; for everyday calling, messaging and voicemail, Teams Phone may be enough.

Then create the users and extensions from your discovery sheet. For a quick look at the product your customers will use, see the hosted PBX your customers use.

How do you connect the customer's SIP trunk and numbers?

On a bring-your-own-trunk platform, external calls run over a SIP trunk from the customer's chosen carrier. The carrier handles numbers and outside calls.

SessionPBX is bring-your-own SIP trunk. You can connect any SIP-compliant carrier by IP or by credentials, whichever the carrier prefers. Stored SIP trunk credentials are encrypted with AES-256-GCM, and SIP signalling, messaging and the admin portal use TLS. SessionPBX doesn't supply numbers or lines: your carrier bills for numbers and calls.

Work through the trunk in this order:

1. Confirm the carrier and the account. Use the trunk the customer already has, or one you arrange with a carrier for them. If you're choosing one, our guide to choosing a SIP trunk provider for hosted PBX lists what to check.
2. Register the trunk. Enter the IP or credential details from the carrier and confirm the trunk registers.
3. Map each number to a route. Give each inbound number a destination: a person, a group, a queue or a call flow.
4. Set the outbound caller ID. Decide which number each user or team shows when they call out, and confirm the carrier allows it.
5. Plan any number move with the carrier. If the customer's numbers are moving from one carrier to another, the move is a carrier process between the losing and gaining carrier. Our number porting checklist explains what the carrier will ask for.

Allow time for the carrier's number move, and don't book cutover until the carrier has confirmed a date. Until then, the customer's numbers keep ringing on their old system, which is exactly what you want.

How do you build and test call flows before go-live?

Call flows decide what happens to every inbound call. Build them from your discovery sheet and test them with the customer before any real caller reaches them.

On SessionPBX, call flows are a Teams Business feature. The Visual Call Flow Designer lets you connect menus, schedules, announcements, ringing destinations and voicemail in a visual editor. You save changes as a draft, validate the flow and publish when it's ready. The draft step makes testing safe.

A simple build order works for most customers:

• Start with opening hours. Set the customer's hours for each day and their time zone, then decide where calls go when they're closed.
• Add the main menu, if there is one. Keep options few and plain, in the customer's own words.
• Point each option at a destination. A person, a ring group, a queue or voicemail.
• Record or upload greetings and announcements. Use the customer's wording, and keep messages short.
• Decide what happens on no answer. Every path should end somewhere sensible, never in silence.

Then sit down with your sign-off contact, open the flow on screen and walk through each path: in hours, out of hours, each menu option, no answer and holidays. Make changes in the draft, validate again and only then publish. Our guide to visual call flow design for small businesses has more on keeping flows simple.

How do you roll out the apps to every user?

The app rollout is when most users meet their new phone system, so make it painless.

On SessionPBX, you invite people by email from the admin portal. Mobile users configure the app with a QR code and desktop users with a setup link, so users don't type SIP settings. Setup emails can carry the customer's branding: app logo branding is included with Teams Business and is an add-on on Teams Phone. Users run the softphone apps for desktop and mobile on Windows, macOS, iOS and Android, and the same account works across all four platforms.

Plan the rollout in three steps:

1. Send invites in batches you can support. Start with your contact and a few willing users, then invite everyone else.
2. Give users a short guide. Which app to install and what to do with the QR code or setup link.
3. Track sign-ins. Check that every user has signed in on at least one device before cutover.

Treat provisioning as a security task too: invites should reach only the right person. Our guide to secure softphone provisioning for MSPs covers the controls to put in place.

How does the trial turn into a paid subscription?

The commercial step needs planning too, or the customer's service is at risk just as they start to rely on it.

On SessionPBX, the trial terms for partner customers are set out on the Partner Programme page: New partner customer tenants receive a 30-day trial on hosted and self-hosted deployments, subject to your concurrent trial allowance. A partner administrator must explicitly purchase the subscription to continue service.

That means the purchase is your job, not the customer's. Build it into the runbook:

• Note when the trial started against the customer, on the same sheet as discovery.
• Name the partner administrator who will make the purchase, and a backup.
• Agree the plan with the customer before the trial ends, so you buy the right one first time.
• Purchase before cutover, so the customer goes live on a paid subscription rather than a trial.
• Keep track of how many customers are on trial at once if you're onboarding several together.

Your own price to the customer should already be agreed before onboarding starts. If you still need to work it out, our guide to MSP pricing for hosted voice shows how to cover onboarding hours as a cost line. For the customer's side of the same step, share our hosted PBX trial checklist, which explains what they should check before they commit.

What happens on cutover day and in the handover pack?

Cutover day is when the customer's numbers start ringing on the new phone system. If the earlier stages are done, it should be quiet. Avoid the customer's busiest periods.

Cutover-day checklist

1. Trunk live and routes tested. The SIP trunk is registered and every inbound number reaches its route.
2. Call flows published. The final, customer-approved version is live, not a draft.
3. Every user signed in on at least one device. Anyone missing has been chased or has a plan.
4. Voicemail greetings recorded. Personal and shared mailboxes have the right greeting.
5. Number move confirmed by the carrier. If numbers are moving carrier, the carrier has confirmed the move is complete.
6. Customer contact on standby. Someone at the customer is ready to test real calls and report problems.

After the switch, place a few real inbound calls with the customer, in hours and out of hours, and check outbound caller ID.

Then send the handover pack.

• Who to call for support, how to reach your team and what details to give.
• How to add or remove users, and who at the customer is allowed to ask.
• Voicemail and missed calls: where users find messages and how they see calls they missed.
• Where the call flows live, with a copy of the agreed routes and who can request changes.
• Carrier details: which carrier holds the numbers and who manages that account.

If the customer is leaving an on-site phone system rather than another hosted one, the cutover has extra steps, such as retiring old equipment and lines. Our guide to migrating from on-premise PBX to hosted PBX covers that PBX migration in detail. The same handover pack works for any VoIP migration.

Onboarding stages, owner and output

Ready to run this runbook for your own customers? Applications to the SessionPBX Partner Programme are reviewed by our team. Once approved, we set up your partner pricing and partner workspace in SessionCloud, and you create your first customer project. Become a SessionPBX partner.

FAQ

How long does onboarding a customer onto hosted PBX take?

It depends on the number of users, how complex the call flows are and how long the carrier takes to move any numbers. Plan the stages, then set the cutover date once the carrier has confirmed its part.

Can the customer keep their phone numbers?

Usually, yes. The numbers stay with the customer's carrier, or move between carriers through the carrier's own porting process. Our porting checklist above explains what the carrier will ask for. You then route each number on the customer's phone system.

Do users need new phones?

Users make and take calls in the softphone apps on Windows, macOS, iOS and Android, so most can use the computers and mobiles they already have. Check each person's devices during discovery.

Who owns the customer's phone system after onboarding?

You do. On SessionPBX, each customer gets their own SessionPBX project under your partner account. You create it, you own it, and you manage extensions, numbers, the SIP trunk and call flows for that customer.

How long is the partner trial for a new customer?

New partner customer tenants receive a 30-day trial on hosted and self-hosted deployments, subject to your concurrent trial allowance. A partner administrator must explicitly purchase the subscription to continue service. Full partner terms are on the Partner Programme page.