My Business Phone Stopped Working After NBN: What to Do Right Now

Business phones going dead after an NBN migration is one of the most common -- and most avoidable -- small business communication crises in Australia. This guide covers exactly what caused it, what the quick fixes are (and why they do not fully solve the problem for a business), your real options, and how to get your phone number back. If you are reading this because your phones are down right now, start at the Quick Fix section below.

What Probably Happened

When Australia's copper phone network (the PSTN) was switched off in 2025, all phone services had to move to NBN or another internet-based system. Most residential and small business customers were moved by their ISP -- but the phone service was often treated as a secondary concern.

Here is the most likely explanation for what happened to your phone: your old copper phone line was disconnected as part of the NBN migration, and either the phone service was not set up on the new NBN connection, or it was set up but your existing handset or phone system is not compatible with the new setup.

In plain terms: the old phone network your phones were plugged into no longer exists. Your internet probably works fine because that was migrated. The phone line was a separate connection that needed its own migration.

The Quick Fix: Check If Your ISP Set Up a Phone Service

Many NBN plans come with an optional phone service that runs through the NBN connection. Your ISP may have set this up -- or may not have, depending on your plan.

Here is how to check:

• Look at your NBN modem or router. Most NBN modems have one or two phone ports on the back (sometimes labelled "Phone 1" and "Phone 2", or "Tel"). These are different from the ethernet ports.
• If your modem has phone ports, try plugging a standard handset directly into one of those ports. If you get a dial tone, your ISP did set up a phone service -- your existing phone equipment just is not configured to use it.
• If there are no phone ports on your modem, your ISP plan may not include a phone service. Call your ISP and ask specifically whether voice (phone) service is included in your NBN plan and whether it has been set up.

The device that makes a standard phone work on an NBN connection is called an ATA (Analogue Telephone Adapter). Some modems have one built in. Others use a separate small device that plugs into the modem. If your ISP gave you one of these and it is not connected, that is why your phone is not working.

For more on how ATAs work, see ATA Adapters for Business: What They Are and When They Are Not Enough.

Why the Quick Fix Is Not a Real Solution for Business

If you plugged into the modem's phone port and got a dial tone, you technically have a working phone again. But for a business, this is a band-aid, not a solution. Here is why:

• One line only. Most ISP phone services give you one phone line. If two people are on calls at the same time, one gets a busy signal. For a business with more than one person, this is a problem.
• No business features. ISP phone services are designed for residential use. No hold music. No auto-attendant. No ring groups. No call recording. No voicemail to email. No after-hours routing. These features are standard on business phone systems but not on ISP voice services.
• The ISP controls everything. If they change their voice product or discontinue it, your phone goes down again. You have no control over the service, its quality, or its continuity.
• Call quality is often poor. ISP voice services are not prioritised for quality. If your internet is busy (staff downloading files, video calls), your phone call quality will suffer.
• Your number may not be portable. Some ISP-assigned phone numbers are harder to port away from the ISP than a standard business number. Check this before you rely on it.

For a business, the right fix is a proper phone system -- not just a dial tone through a modem port.

Your Real Options: A Proper Business Phone System

The right replacement for your old copper phone line is a hosted VoIP system -- sometimes called a cloud phone system or cloud PBX. Here is what that means in plain language:

• Your phone calls travel over your existing internet connection (NBN) rather than a dedicated phone line
• The phone system itself -- the bit that manages calls, holds, transfers, ring groups -- lives on a server managed by your provider, not a box in your office
• You can have as many simultaneous calls as you need (limited only by your internet connection)
• You get features like hold music, voicemail to email, an auto-attendant ("press 1 for sales"), ring groups, call recording, and softphone apps for mobiles
• You keep your existing phone numbers via a process called number porting (more on this below)

For most small businesses, setup takes less than a week, and some providers offer same-day or next-day provisioning if you do not need number porting right away (you can use a temporary number while the port is in progress).

Cost is typically $30 to $55 per user per month including GST for a business plan. Use the VoIP Cost Calculator to estimate your total cost based on your team size and the features you need.

To understand what to look for in a hosted VoIP setup, see Setting Up VoIP on NBN: A Step-by-Step Guide for Australian Businesses.

Can You Get Your Old Number Back

Yes, usually -- but act quickly. Phone numbers in Australia can be ported (transferred) from one provider to another under ACMA rules. If your old number was on a copper line that has now been disconnected, there is a window during which the number can still be recovered and ported, but it narrows over time.

Here is what to do right now:

• Call your old phone provider (whoever you paid for the copper line) and tell them you want to port that number to a new service. Do not ask them to cancel -- ask about porting.
• Alternatively, sign up with a new VoIP provider and give them your old number. They will check portability and initiate the port for you.
• Number porting typically takes 5 to 10 business days for standard geographic numbers. It takes longer if the number is on a recently cancelled or disconnected service.
• If too much time has passed since disconnection, the number may have already been returned to the number pool and allocated to someone else. In that case, you cannot recover it. This is why acting quickly matters.

For a full breakdown of how porting works and what can go wrong, see Number Porting in Australia: What Businesses Need to Know.

Emergency Option: Forward Your Number to a Mobile Right Now

If your phone is down today and you cannot wait a week for porting and setup, here is an immediate stopgap:

• If your number is still technically active with your old provider (even if the physical line is disconnected), call them and ask for unconditional call forwarding to your mobile number. This routes all incoming calls to your mobile while you sort out the permanent fix.
• If you need a new number temporarily, some VoIP providers can provision a new number and softphone app within hours, so your business has a working phone line the same day while the porting process runs in the background.
• Update your Google Business profile, website, and any directories with a note that calls are being handled on a temporary line while your system is being upgraded -- this maintains customer trust during the gap.

Will Your NBN Connection Handle Business Calls

Before setting up any VoIP system, check that your NBN connection is fast enough and stable enough for business calls. The key number is upload speed, not download speed. Each simultaneous call uses roughly 100 Kbps of upload bandwidth.

A business with 4 staff who might all be on calls at once needs at least 400 Kbps of stable upload capacity -- plus headroom for everything else on the network. Most NBN plans well beyond this on paper, but the real-world figure depends on your connection type, your ISP, and how loaded the local network is during business hours.

Use the VoIP Bandwidth Calculator to check whether your specific connection and team size combination is safe for VoIP before you commit to a provider.

What Most Businesses Get Wrong in This Situation

Mistake 1: Accepting the ISP's bundled phone service as a permanent fix. Getting a dial tone from the modem port feels like the problem is solved, but it is not. One line, no business features, no control, often poor quality. The quick fix is fine for a day while you assess your options -- it should not become your permanent phone system.

Mistake 2: Cancelling everything before checking on your number. When your phone stops working, the instinct is to cancel whatever you are paying for and start fresh. But if your old number is still technically active with your old provider, cancelling before you initiate a port means you lose the number. Call about porting first, always.

Mistake 3: Waiting too long to act on the number. Phone numbers that are disconnected are not held forever. The longer you wait after a disconnection, the higher the risk the number goes back into the allocation pool. If getting your old number back matters to you -- and for most businesses it does, because it is on cards, signage, and customer records -- act on porting within days, not weeks.

Your Next Steps

• Right now: check if your modem has phone ports and try plugging a handset in to see if you have a dial tone (quick test only -- not a permanent fix)
• If phones are completely down: set up call forwarding to your mobile as an emergency stopgap
• Contact your old provider about your phone number and porting options before doing anything that might cancel the number
• Run the Bandwidth Calculator to confirm your NBN can handle business calls
• Use the Cost Calculator to estimate what a proper business phone system will cost for your team size
• Get a provider recommendation matched to your situation and timeline

How long will it take to get my business phone working properly again?

If you do not need to port your existing number, a new hosted VoIP system can be set up within 1 to 3 business days. If you need to port your existing number from your old provider, add 5 to 10 business days for the porting process. Many providers will provision a temporary number immediately so you have a working phone while the port is in progress.

My ISP says my phone service is included in my NBN plan. Why is it not working?

ISP phone services on NBN require either a modem with a built-in ATA (phone port on the back of the modem) or a separate ATA device. If your modem has phone ports but they are not working, the service may not have been provisioned correctly. Call your ISP and ask them to check the voice service configuration on your account. Ask specifically whether the voice service is enabled and whether the ATA on your modem is provisioned.

Can I keep my existing phone number?

Yes, in most cases. Australian phone numbers can be ported from one provider to another. If your old number was on a copper line that has been disconnected, act quickly -- the number can usually still be recovered and ported, but the window closes over time. Tell your new VoIP provider the number you want to keep and they will handle the porting process. Do not formally cancel your old service before the port is confirmed complete.

How much does it cost to set up a proper business phone system on NBN?

For a small business, expect $30 to $55 per user per month including GST for a hosted VoIP plan. This typically includes your phone number, unlimited local and national calls, and business features like hold, transfer, voicemail to email, and an auto-attendant. You may also need handsets ($90 to $350 each) if your existing phones will not work with VoIP. Use the Cost Calculator for a figure based on your specific situation.

Will VoIP calls sound as good as my old copper phone line?

With a good NBN connection and a provider that prioritises call quality, VoIP calls are equal to or better than copper in most cases. The risks are an unstable connection, a congested network during business hours, or a router that does not prioritise voice traffic. Your provider should help you check and configure this. If call quality matters -- and for a business it always does -- ask any provider you are considering what their uptime SLA and call quality guarantees are before signing.

What if my NBN connection is not fast enough for VoIP?

Most modern NBN connections are fast enough for business VoIP -- the issue is usually stability and upload speed rather than raw speed. If your current NBN plan has poor upload speeds or frequent dropouts, you may need to upgrade your plan or switch to a business-grade NBN service (which typically comes with a faster response SLA and better traffic prioritisation). Run the Bandwidth Calculator first to identify whether this is actually an issue for your team size.

For a broader look at how PSTN shutdown affected Australian businesses and what the industry-wide picture looks like, see PSTN Shutdown Australia: What Businesses Need to Know.