Most Australian businesses are still running phone systems installed five to ten years ago. They work, mostly, which is why they survive. But the maintenance contracts get dearer, the parts get scarcer, and eventually someone has to answer the question: what do we replace this with?

That’s where it gets confusing, because the market answers with a pile of acronyms. Here are the actual options, in plain terms, and who each one genuinely suits.

Option one: keep the PBX, replace the lines

If your PBX is reasonably modern and supports SIP, you can keep the whole system and just swap the expensive legacy lines for SIP trunks, which carry calls over your internet connection instead of dedicated copper. Same handsets, same call flows, materially smaller bill. Line rental savings alone often run to hundreds a month.

This is the right move when the PBX still has life in it, the handset investment was recent, or your call routing is complex and hard-won. It’s a cost fix, not a modernisation, and there’s nothing wrong with that. The one prerequisite: your internet connection has to be good enough to carry voice cleanly, with quality-of-service configured, or you’ll trade line rental for call complaints.

Option two: hosted PBX

Here the box in the comms room goes away entirely. The phone system runs in the provider’s cloud, you pay per user per month, and handsets plug into the network wherever they are. Multi-site businesses get one system across every location. Nobody maintains hardware, and scale moves with headcount in either direction.

Platforms like 3CX sit in this family too, with a twist: 3CX is software you can host wherever you like, licensed by concurrent calls rather than per user, which can make it notably cheaper for businesses with many staff but few simultaneous calls. The trade-off is that someone has to own the platform’s configuration, so it best suits businesses that have IT capability and want the control.

Option three: calling inside Microsoft Teams

If your staff already live in Teams, the phone system can simply become part of it. Add PSTN calling to Teams and the separate phone platform disappears: one app for chat, meetings and phone calls, on the laptop and the mobile, with numbers, queues and voicemail all inside it. Licensing runs per user per month on top of your Microsoft agreement, and for organisations already paying for Microsoft 365, the incremental cost frequently undercuts running any separate voice platform at all.

There are a few routes to connect Teams to the phone network, ranging from Microsoft’s own calling plans to carrier programs like Operator Connect. They differ meaningfully in cost and flexibility, and the right one depends on your carrier situation and call volumes. (We’ve written more on that in our Operator Connect piece.)

How to actually decide

The pattern from the migrations we run: businesses with a solid recent PBX keep it and swap lines. Businesses with multiple sites, an end-of-life system, or no telephony expertise in-house go hosted. Businesses already deep in Microsoft 365 increasingly fold voice into Teams and stop thinking about phone systems altogether. And a hundred-line business moving off legacy line rentals saves tens of thousands a year under any of the three.

The wrong way to decide is on a provider’s brochure, because every provider’s brochure concludes you need what they sell. The costs that actually matter are your real ones: what the current system truly costs (including the maintenance contract and the hardware nobody counts), what your call patterns look like, and what your internet can carry. We do that analysis carrier-agnostically, then run the migration end to end: numbers ported, cutover staged, nobody’s Friday morning interrupted. Talk to us when the old system’s time is up, or before the next maintenance renewal locks you in for another year.