Add Hosted PBX to SIP Trunks: Guide for SIP Trunk Providers

Tom Reed · Updated 28 October 2026

If you're already a SIP trunk reseller, adding a hosted PBX lets you sell the whole phone system, not just the lines, while numbers and external calls stay on your own trunks. You set the price and invoice the customer, your logo goes on the apps their team uses, and the main changes are in onboarding and support.

This guide is for any internet telephony service provider (ITSP) or VoIP provider that sells SIP trunks to businesses, and for MSPs and IT resellers who resell trunks today. Where we mention SessionPBX, Teams Phone and Teams Business are SessionPBX plans, not Microsoft Teams.

Why should a SIP trunk reseller add a hosted PBX?

A trunk gives a business its connection to the phone network. The phone system on top decides who rings, what callers hear and which apps the team uses. When you only sell the trunk, someone else owns that layer and the day-to-day relationship that comes with it.

Adding a hosted PBX moves you from selling lines to selling the phone system. Your customer gets calling, apps, call flows and admin in one place, from the provider that already carries their calls. You become the first call for anything to do with their phones, not just the trunk.

It also makes the offer easier to explain. Instead of "here are your trunks, find a phone system", you can offer a complete hosted VoIP service: trunks you know, a hosted PBX you run for them, and apps for every user. For a sip trunking reseller, that's a natural next step rather than a new business.

Think about the conversations you already have. Customers ask which phone system works with your trunks, how to set up menus and opening hours, or which app their staff should install on a laptop. Each of those questions is a chance to supply the answer yourself instead of pointing them elsewhere. When the phone system comes from you, every change to users, routes or greetings is a reason for the customer to talk to you, not to another supplier.

Selling trunks only vs trunks plus hosted PBX

Do numbers and calls stay on your own SIP trunks?

Yes. A SIP trunk connects a phone system to the phone network over the internet, and on a bring-your-own-trunk platform that connection stays yours.

SessionPBX is bring-your-own SIP trunk. You can connect any SIP-compliant carrier by IP or by credentials, whichever your network prefers. Your carrier bills for numbers and calls, and internal calls between team members are included. There are no bundled minutes and no per-minute markup from the platform, and you can switch trunks in the admin portal whenever you need to.

That means your trunk business keeps working exactly as it does today. You keep supplying the trunk, the customer's numbers stay where they are, and the hosted PBX sits on top. If a customer wants another carrier for some sites, they can bring it too. Our guide to choosing a SIP trunk provider for hosted PBX shows what customers check on the trunk side, and our guide on how many SIP channels you need helps you size each customer's trunk.

Who bills the customer?

You do. On the SessionPBX Partner Programme, you set your own price and invoice your customer on your own terms. SessionTalk bills your partner organisation for each customer subscription, and there are no commissions to chase and no payouts to wait for.

So the customer sees a single provider for trunks and phone system: you. You decide how to package the trunk and the hosted PBX together, and how to present it on your own invoice. Partner pricing is shown on the Partner Programme page.

Before you quote your first customer, decide a few things in advance:

• What's in the package. Trunk and phone system together, or the phone system as an extra on top of an existing trunk contract.
• How you price change requests. New users, new call flows and new numbers will come up, so decide what's included and what isn't.
• Who signs the order. Keep one named contact at the customer for approvals, especially for call flow changes.

For ideas on structuring the offer, see our guides to MSP VoIP pricing and margin and packaging hosted PBX for MSPs and telecom resellers.

Should you run it hosted or on your own servers?

You have two options, and many trunk providers will use both.

Hosted. SessionTalk hosts and maintains SessionPBX in the UK (London), the US (New York) or Singapore. You choose where each customer is hosted, and each region has its own database. Each customer gets one SessionPBX project, created and owned by you in SessionCloud. This suits smaller customers and providers who don't want anything to run.

Self-hosted. Approved partners can run SessionPBX on their own servers, with many customer tenants on one platform and every customer kept separate. If you already run your own voice infrastructure, this keeps the phone system on the network you already manage, next to your trunks. Server, hosting and network costs are yours.

A useful rule of thumb: put small customers on the hosted platform, with nothing for you to run, and self-host where you want the system on your own infrastructure. Our guide to multi-tenant PBX for MSPs explains how running many customers on one platform works.

Whichever you choose, the customer's experience is the same: the same softphone apps, the same admin portal and the same trunks underneath. The difference is who runs the platform. If your team already operates voice servers and wants everything on its own network, self-hosting is worth a serious look. If you'd rather spend your time selling and supporting customers, start hosted and decide on self-hosting later.

How does your logo appear on the apps?

With app logo branding, you upload a logo and in-app product name once in the portal. Branding is applied inside the standard SessionCloud Softphone app at runtime, and every team member's softphone picks it up the next time they sign in or scan their QR code. The same brand shows on Windows, macOS, iOS and Android.

Setup emails carry the same branding, with a QR code for mobile or a setup link for desktop, so your customer's staff see your name from the first invitation. App logo branding is included with Teams Business and is an add-on on Teams Phone.

For a closer look, see the softphone apps your customers' teams use, and our post on a cloud softphone platform with branded SIP apps.

What changes in support when you sell the PBX as well as the trunk?

Today your support desk handles trunk and carrier issues. Once you sell the phone system, you also own call flows, extensions and the apps on each user's device. Plan for that before your first customer goes live.

The good news is that you already know the hardest part. Trunk faults, registration problems and caller ID questions are familiar ground for a trunk provider. What's new is the layer above: who should ring when a call comes in, what callers hear out of hours, and why a user's app isn't ringing.

Build a simple triage split, so every ticket lands in the right place quickly:

• Trunk and carrier. Registration, inbound numbers, outbound caller ID and call quality on the trunk.
• Platform. Call flows, opening hours, groups, queues, voicemail and user settings in the admin portal.
• User device. App sign-in, notifications, headsets, microphones and the user's network.

Security is part of support too. On SessionPBX, SIP signalling, messaging and the admin portal use TLS, stored SIP trunk credentials are encrypted with AES-256-GCM, and IP access controls and automated blocking help protect against repeated login attempts and toll fraud. Our guide to VoIP toll fraud prevention covers the controls to review with each customer.

A few habits make support easier from the first customer:

• Keep a record per customer. Users, extensions, call flows and the trunk each customer uses, kept somewhere your whole team can find it.
• Agree change control. Decide who at the customer can ask for changes, and confirm changes in writing.
• Train your first-line team. Make sure they can tell a trunk fault from a call flow question from an app problem, using the split above.

For the per-customer runbook, from discovery to cutover day, use our MSP onboarding checklist for hosted PBX.

Before you add hosted PBX to your SIP trunk offer

• Confirm your trunks connect by IP or by credentials.
• Decide between hosted, self-hosted or both.
• Choose a hosting region for each hosted customer.
• Set your own pricing and how you'll bill the customer.
• Prepare your logo and in-app name for app logo branding.
• Write a support split: carrier, platform and user device.
• Review toll-fraud controls with your team.
• Choose a first pilot customer.
• Get an onboarding runbook ready.
• Apply on the Partner Programme page.

How do you get started as a partner?

Start by applying to the SessionPBX Partner Programme. You don't need a SessionCloud account to apply, and every application is reviewed by our team. Partner pricing and workspace access are switched on after approval, and then you create your first customer project.

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.

If you're comparing programmes, our guide on how to choose a VoIP reseller program lists the questions to ask. To see what your customers get, look at the hosted PBX your customers use.

Ready to sell the phone system as well as the trunk? Apply to the SessionPBX partner programme.

FAQ

Can customers keep using my SIP trunks with the hosted PBX?

Yes. SessionPBX connects any SIP-compliant carrier by IP or by credentials, so your customers' external calls keep running over your trunks.

Does the platform charge per-minute for external calls?

No. There are no bundled minutes and no per-minute markup. Your carrier bills for numbers and calls, and internal calls between team members are included.

Can I run the PBX on my own servers?

Yes. Self-hosted SessionPBX is available to approved partners, who can run many customer tenants on their own servers, with every customer kept separate.

Will my customers see my brand?

Yes. App logo branding puts your logo and in-app product name on the softphones, and setup emails carry the same branding. It's included with Teams Business and is an add-on on Teams Phone.

Do I need a SessionCloud account to apply?

No. Every application is reviewed by our team, and partner pricing and workspace access are switched on after approval.

Who owns the customer relationship?

You do. You create and own each customer's project, set your own price and invoice the customer on your own terms.