Most businesses choose a phone system on features and then spend three years regretting the choice on support and billing. The feature lists of carrier hosted PBX, Microsoft Teams Phone and 3CX overlap almost completely at the 10 to 200 staff mark. What actually separates them is cost structure, who picks up the phone when calls stop working, how much of your call flow you are allowed to change yourself, and how hard it is to leave.
A hosted PBX is a phone system owned and operated by a carrier or telco in their data centre and sold to you per user per month, with the carrier controlling the platform, the numbers and the fault path. That single sentence explains most of the differences that follow.
This post assumes you already understand how VoIP actually works for an Australian business and that you can read up on Microsoft Teams Phone in detail separately. This is the choosing part.
The three options, described honestly
Carrier hosted PBX. The carrier owns everything: the platform, the trunks, the numbers, the handsets in most cases, and the support desk. You get a portal with limited configuration rights. Changes that the portal does not cover go through the carrier as a service request.
Microsoft Teams Phone. Teams Phone is a licensed add-on that turns Microsoft Teams into your phone system. Microsoft Learn is explicit that a Teams Phone licence on its own does not make calls: the user account must be licensed with Teams Phone and also equipped with a public switched telephone network solution. There are four ways to supply that: Microsoft Calling Plan, where Microsoft is your carrier; Operator Connect, where a certified Australian carrier plugs into your tenancy; Teams Phone Mobile, where a mobile SIM number becomes the Teams number; and Direct Routing, where any carrier connects through a certified session border controller that you or your provider run.
3CX. 3CX is a software PBX you or your IT provider deploy and administer, either hosted by 3CX, on-premise, or self-hosted on a cloud provider such as Azure, AWS, Google or DigitalOcean. You bring your own SIP trunk and your own numbers. Read the fuller treatment of 3CX for Australian business if that is the direction you are leaning.
Cost is a structure question, not a price question
The three models charge on different units, and that is what determines whether the bill grows with you or sits still.
Hosted PBX is per user per month, usually on a fixed term. Every new hire is a new line item. The upside is that the number is predictable and includes the platform, the support and often the handset.
Teams Phone is per user per month for the Teams Phone licence, plus whatever your PSTN option costs. Calling Plan bundles minutes from Microsoft. Operator Connect is a separate contract with the carrier. Direct Routing means you pay for trunks from a carrier and for the session border controller, physical or virtual, that sits between them and Microsoft.
3CX licenses on simultaneous calls rather than users, and 3CX publishes its pricing on that basis as an annual subscription with hosting and support as separate additions. A business with 60 staff who are rarely all on the phone at once buys a much smaller licence than a 60-seat per-user model implies. Trunks and numbers are bought separately from an Australian carrier, so there are at least two invoices.
The trade-off is real. Per-user pricing is expensive at scale but requires no thinking. Simultaneous-call pricing is cheaper for most SMBs but you have to size it, and sizing it wrong means busy signals at your peak hour.
We are not publishing prices here because they change and because they depend on your trunk provider. Ask for the total of every line item over a three year term, not the headline per-seat rate.
Who answers when it breaks
This is the question most buyers skip and most regret.
With a carrier hosted PBX, the carrier is the single point of contact and the single point of blame. That is genuinely valuable when something is wrong at the trunk level. It is much less valuable at 9am on a Monday when the fault is a misconfigured queue and you are in a ticket queue behind a national customer base.
With Teams Phone, the support path depends entirely on which PSTN model you chose. Microsoft Learn sets this out plainly: with Calling Plan, support is Microsoft; with Operator Connect and Teams Phone Mobile it is the operator plus Microsoft; with Direct Routing it is the operator, the SBC vendor and Microsoft. Three vendors in the fault path is three vendors who can each say the problem is upstream.
With 3CX, whoever deployed it owns it. If that is a competent local provider, you get someone who can log into the PBX, look at the call logs and fix a routing rule the same morning. If it is a provider who set it up once and moved on, you own a phone system nobody understands.
Ask any provider quoting you voice a direct question: when a call fails, whose console do you open, and how fast. Then ask whether they hold the consumer protection obligations that come with reselling voice, because a provider who resells you a phone service in their own name is taking on regulated responsibilities under the Telecommunications Act, not just a margin.
For our part, TechAssist complies with the TCP Code and is a member of the Telecommunications Industry Ombudsman scheme, which means that if we cannot resolve a voice complaint you have a free and independent external umpire rather than only a commercial argument with us.
Reception, queues and the front desk
If you have a receptionist, this section decides the outcome.
Teams Phone handles auto attendants and call queues through resource accounts, and it does it well enough for most businesses. What it does less well is the classic reception workflow: a busy lamp field showing who is on a call, blind and attended transfers done in one motion, and a physical handset with programmable keys that a receptionist can drive without looking. It is improving, but a Teams-native front desk is a different job to the one your receptionist has been doing for a decade.
Carrier hosted PBX and 3CX both come from the traditional PBX lineage and handle this natively, with supported desk phones and presence panels.
The honest trade-off: Teams Phone is the better answer for a business where nobody has a dedicated reception role and calls land directly on individuals. It is the weaker answer for a practice, a clinic, a wholesaler or a trades business where one person triages every inbound call.
Mobile and remote staff
All three do mobile apps and softphones. The difference is what the staff member has to open.
Teams Phone wins outright if your staff already live in Teams all day, because there is one application and one presence state. A call, a chat and a meeting are the same window.
3CX and hosted PBX both provide iOS, Android and desktop apps, which means a second application and a second presence state to keep in sync. 3CX partially closes this with Microsoft 365 and Google Workspace integration for directory and presence.
If your field staff answer on mobile and never sit at a desk, Teams Phone Mobile is worth investigating, because it makes the mobile SIM number and the Teams number the same number.
Integration with the rest of your stack
Teams Phone integrates with Microsoft 365 by definition, and with Entra ID for identity, licensing and conditional access. That is the strongest argument for it in a Microsoft-committed business.
3CX integrates with Microsoft 365 and Google Workspace for user provisioning and contacts, and has a CRM integration layer for call popping and click to dial. It also supports Teams Direct Routing integration so Teams users and 3CX extensions can call each other, though 3CX documents this as available on Enterprise and AI Edition at 16 simultaneous calls and above, and it requires an SSL certificate from a Microsoft-approved certificate authority, a dedicated FQDN and port 5062 open on your firewall. It is not a checkbox.
Carrier hosted PBX integration varies enormously by carrier and is usually the weakest of the three. Ask for the specific integration by name before you assume it exists.
Emergency calling deserves a separate look
If you go the Teams Phone route, look carefully at how Triple Zero calls carry your location. Microsoft Learn’s comparison table shows registered address for emergency calling as included and Teams admin managed with Calling Plan, optional and operator managed with Operator Connect and Teams Phone Mobile, and not supported with Direct Routing. Dynamic location information is supported across all four but requires additional configuration on Direct Routing.
For a single-site business this is a conversation. For a business with staff spread across sites or working from home, it is a safety issue and it belongs in the decision, not in the go-live checklist.
Number porting is the same problem in all three
Your existing numbers are portable. The ACMA has declared local numbers a portable service, and the process between carriers is governed by the Local Number Portability code, currently C540:2023, published by the Australian Telecommunications Alliance. That code sets minimum standard hours of operation, activation targets and timeframes.
What differs is who drives it. A hosted PBX carrier will normally run the port for you as part of onboarding. With Teams Phone on Operator Connect, the operator does. With Direct Routing or 3CX, your trunk provider or your IT provider does.
Two rules regardless of platform. Do not cancel the old service until the port completes, because a disconnected number is far harder to recover than a ported one. And check whether every number you think you own is actually on the account you think it is on, before you sign anything.
Lock-in is the cost you pay later
Rank the three by how expensive it is to change your mind.
Carrier hosted PBX is the highest lock-in. The platform, the trunks and often the handsets are all the carrier’s, usually on a fixed term, and leaving means a full replacement plus a port.
Teams Phone lock-in depends on the PSTN model. Calling Plan ties numbers to Microsoft. Operator Connect ties them to that operator. Direct Routing is the least locked in of the Teams options because you can change carrier without touching Teams.
3CX is the lowest lock-in on paper: your trunk, your numbers, your choice of hosting, annual rather than multi-year licensing. In practice the lock-in moves to the provider who configured it, which is why documentation matters more here than anywhere else.
If you are X, choose Y
If your business runs on Microsoft 365, calls land on individuals rather than a switchboard, and staff are mobile: choose Teams Phone. Trade-off: reception and queue handling is functional rather than excellent, you take on a licence per user, and you need to make a deliberate decision about emergency calling.
If you have a receptionist or a front desk that triages every call, or you run queues that matter to revenue: choose 3CX. Trade-off: someone has to own and administer it, so it is only the right answer if you have an IT provider who will actually log in and maintain it, and you need to size simultaneous calls correctly.
If you have no internal IT, no IT provider, and you want one invoice and one number to ring: choose a carrier hosted PBX. Trade-off: you will pay more per seat, you will wait in a national support queue, and changing your mind in two years is expensive.
If you are running Microsoft 365 but need real queue and reception behaviour: run 3CX and connect it to Teams via Direct Routing. Trade-off: this is the most capable option and the most complex, and 3CX gates it behind Enterprise or AI Edition at 16 simultaneous calls and above.
One thing that applies to all four answers: the phone system is only as good as the internet service underneath it. If your connection has no committed performance class and no failover, no phone system will fix a bad call. If you are also planning a fit-out, order the carrier service before anything else, because it has the longest lead time of anything in the project.
Book a 30 minute call with TechAssist and we will map your current call flow, count your genuine simultaneous call peak and tell you which of these three fits, including when the answer is to leave your existing system alone. Call 1300 028 324 or use the form at https://techassist.au/contact/. Bring your last two phone bills and a list of your numbers.
