How to Switch Hosted PBX Providers: Cutover Checklist

Tom Reed · Updated 1 November 2026

Switching hosted PBX providers is safe when you plan it as a cutover, not a rip-and-replace. Check the old contract's notice terms, export users, extensions and call flows, keep or move the SIP trunk, build the new system in parallel and move the numbers last, through the carrier. For an MSP or reseller, the switch is also the moment the customer project, billing and app branding move under your own partner account, which is what the SessionPBX partner programme is built for.

This guide is written for MSPs, ITSPs, VoIP providers and IT resellers moving a customer off another hosted or cloud PBX provider and onto SessionPBX. It's also useful for the business owner whose MSP is running the switch and wants to know what happens when. It doesn't repeat the carrier's number port process or the new-customer runbook; it links to those where they fit. One naming note before we start: Teams Phone and Teams Business are SessionPBX plans, not Microsoft Teams. SessionPBX is a standalone phone system, and it can be hosted by SessionTalk or self-hosted on your own server if you're an approved partner.

When is it worth switching hosted PBX providers?

Most switches start with a frustration that has been building for a while. Hosted PBX providers differ a lot in how they handle support, how much admin control they hand over and where they host. A customer may be fine with the calls themselves but tired of raising a ticket for every extension change. Common reasons to move include:

• Support that doesn't fit. Simple changes take too long, or nobody on the provider's side knows the customer's setup.
• Not enough admin control. The customer or their MSP wants to add users, change call flows and manage permissions themselves.
• Region. The team wants the phone system hosted closer to where they work.
• Carrier tied to the PBX. The provider bundles the PBX with its own calling service, so changing one means changing both.
• Reselling with your logo. An MSP wants the customer's phone system under its own partner account, with its logo on the apps, instead of referring the customer to someone else's product.

None of these mean the old provider is bad. They mean the fit has changed. Keep the conversation with the customer about what they need next, not about the provider they're leaving. If the customer is actually moving off an on-site system rather than another hosted service, moving from an on-site PBX instead? covers that route.

What should you check in the old contract before you give notice?

Read the contract before anyone gives notice. The terms vary from provider to provider, so don't assume. The points that decide your plan are:

• Notice period. How much notice the old provider needs, and whether it has to be given in writing or through their portal.
• End date. Whether the contract runs to a fixed term or rolls on, and what happens if service carries on past the end date.
• Who holds the numbers. Whether the phone numbers sit with the old PBX provider or with a separate carrier the customer contracts directly.
• Carrier tie-in. Whether the calling service is part of the same contract as the PBX, and what leaving one means for the other.

Write down what you find and agree it with the customer. The notice date is the customer's decision, because it's their contract. Your job as the partner is to make sure the new system is ready before the old one stops, so the safest order is almost always: build first, confirm the cutover, then give notice.

What do you need to export from the old system?

Before you build anything, collect a full picture of how the customer's phones work today. Export what the old provider allows, and where there's no export, take screenshots or write it down. You'll rebuild the setup by hand on the new system, so a clear record matters more than a file format. Gather:

• Users and extensions. Names, email addresses, extension numbers and who needs which permissions.
• Ring groups and queues. Who is in each group, the ringing order and where unanswered calls go.
• Call flows and opening hours. Menus, schedules, out-of-hours routes and any holiday handling.
• Voicemail greetings. Download the recorded greetings and announcements if the old provider lets you, or note the scripts so they can be re-recorded.
• Call recordings. Any recordings the customer wants to keep. Agree this with the customer early, because once the old service ends you may lose access to them.
• Inbound routing. Which number rings which person, group or menu.

Keep this record with the customer's project notes. It becomes the build sheet for the next step and the checklist you test against on cutover day.

Can you keep the same SIP trunk and numbers?

Often, yes. It depends on where the calling service sits.

If the customer's SIP trunk comes from a carrier that is separate from the old PBX provider, you can usually keep it. SessionPBX is bring-your-own SIP trunk and works with any SIP-compliant carrier, so you connect the existing trunk to the new system and the customer keeps their carrier relationship. Stored trunk credentials are encrypted, and TLS protects signalling and messaging.

If the numbers sit with the old PBX provider, they need to move to a carrier the customer chooses, and that carrier handles the number port. The business phone number porting checklist walks through the port itself with the carrier. If the customer needs a new carrier as part of the switch, start with how to choose a SIP trunk provider for a hosted PBX.

Either way, decide the carrier route early. It shapes the whole timeline, because the carrier sets the timing of any port and the old contract sets the notice date.

How do you build the new system in parallel?

Build the new system while the old one is still running, so nothing changes for the customer's callers until you're ready. As the partner, the steps look like this:

1. Create the customer's project. 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.
2. Choose the region. Hosted SessionPBX runs in the UK (London), the US (New York) or Singapore. Pick the one closest to the customer's team.
3. Connect the trunk. Add the customer's SIP trunk from their carrier.
4. Rebuild extensions and call flows. Use your export as the build sheet. Give the business its own SIP domain and familiar, short extensions. On Teams Business, rebuild call flows, ring groups, queues and business-hours routing, upload or record greetings, and set recording and supervision.
5. Invite users by email. Each person gets an email invitation. Manage extensions, seats and member permissions centrally.
6. Set up the apps. Users install the SessionTalk apps on Windows, macOS, iOS or Android. Mobile apps are configured with a QR code and desktop apps with a setup link, so nobody types SIP settings. These are the desktop and mobile apps users install on day one, and the Windows and Mac desktop softphone rollout guide covers getting them onto every laptop.

You also choose how the system runs. With the hosted option, SessionTalk takes care of hosting and maintenance, so you have nothing to run. If you'd rather keep the system on your own infrastructure, self-hosted is available to approved partners only, and lets you run many customer tenants on your own server with every customer kept separate. If the customer wants a managed setup and nothing to look after, a hosted PBX phone system managed for you is the simpler route. For the full new-customer runbook, see MSP customer onboarding for a hosted PBX.

What happens on cutover day?

Cutover is the moment inbound calls start arriving on the new system. Plan it for a quiet time in the customer's week and make sure someone who knows the call flows is available.

1. Point inbound calls at the new system. If the customer is keeping their trunk, change the inbound routes so calls arrive on SessionPBX. If numbers are moving, the carrier completes the port on the date it confirms.
2. Check internal calls. Have users call each other on the new apps, on desktop and mobile, and try hold and transfer.
3. Check real inbound routing. Work through your export: each number, each menu option, opening hours and out-of-hours routes, voicemail and missed-call emails.
4. Fix and recheck. Correct anything that doesn't match the build sheet, then check it again.
5. Keep the old service live until sign-off. Don't cancel anything until the customer confirms calls are working the way they expect.
6. Then give notice. Once the customer signs off, they give notice on the old contract according to its terms.

Expect a few questions from staff in the first days. Short, hands-on help with the app usually settles them. Keep your export to hand in case a routing detail was missed.

Cutover checklist for switching hosted PBX providers

Use this as the shared checklist between you, the customer and the carrier. Reword it for your own process, but keep the order.

How do you move the customer's billing and branding to you?

This is where a switch pays off for a partner. Once the customer is on SessionPBX under your partner account, the relationship is yours.

Billing. You set your own price and invoice your customer. SessionTalk bills your partner organisation for each customer subscription, and you bill the customer on your own terms. There are no commissions to chase and no payouts to wait for. Partner pricing is shown on the partners page and in your partner portal, so check there rather than relying on old quotes.

Branding. App logo branding puts your logo and in-app product name on the softphones your customers use every day. You upload the logo and in-app name once in the portal, and every team member's app picks it up the next time they sign in or scan their QR code. Setup emails go out with the same branding, so the customer's staff see your name from the first invitation to the first call. App logo branding is included with Teams Business and available as an add-on on Teams Phone. Again, Teams Phone and Teams Business are SessionPBX plans, not Microsoft Teams.

Hosting choice. You can put smaller customers on the hosted platform and self-host where you want the system on your own infrastructure. Partner pricing applies to both hosting options.

If you're not yet a partner, applications are reviewed by our team and you don't need a portal account to apply. Become a SessionPBX partner to see partner pricing and start moving customers onto your own account.

FAQ

How long does it take to switch hosted PBX providers?

It depends on two things outside your control: the notice period in the old contract and, if numbers are moving, the carrier's timing for the port. The build itself can run in parallel while both of those play out. Plan backwards from the contract end date and leave room to check everything before giving notice.

Do I lose my phone numbers when I switch?

Not if the carrier ports them properly. If the numbers sit with a separate carrier, they stay where they are and you point them at the new system. If they sit with the old PBX provider, the carrier you choose handles the port. Keep the old service live until the carrier confirms the port is complete.

Can I keep my current SIP trunk?

Yes, as long as it comes from a SIP-compliant carrier. SessionPBX is bring-your-own SIP trunk, so you connect the customer's existing trunk to their new project and keep the carrier relationship as it is. If the trunk is bundled with the old PBX provider, you'll need a carrier of your own first.

Do users need new apps?

Yes. Users install the SessionTalk apps on Windows, macOS, iOS or Android. They don't type SIP settings: mobile apps are set up by scanning a QR code and desktop apps by opening a setup link from their invitation email. With app logo branding, they see your logo and in-app product name from the first sign-in.

Can an MSP move a customer onto its own partner account?

Yes. Each customer gets their own SessionPBX project under your partner account, which you create and own. You manage the customer's extensions, SIP trunk and call flows, set your own price and invoice the customer yourself. Apply through the SessionPBX partner programme to get started.

Can I try it before switching?

If you're using SessionPBX for your own team, you can start a 14-day free trial. Our hosted PBX free trial checklist shows what to test during it. MSPs and resellers moving customers should apply to the partner programme instead, because partner accounts are set up after review.