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

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

Australia's migration from legacy copper services has occurred progressively by area. Most affected fixed-line services had to move to the NBN or another network, but some copper, business, Special Service and alternative-network services were exempt or followed different schedules. Migration was not automatic: affected customers generally needed to arrange replacement internet and phone services through a phone or internet provider.

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.

At many affected fixed-line premises, the legacy phone service has been disconnected, although copper services still operate in some areas and service categories. 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. Some provider-supplied modem/routers and some FTTP connection boxes have phone ports, depending on the NBN access technology and provider setup. These are different from the ethernet ports.
• If your modem has phone ports, try plugging a standard handset directly into one of those ports. A dial tone suggests the voice port has been activated, but make a test call and confirm the equipment, wiring and service configuration before treating the fault as isolated.
• 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. Basic bundled voice services may include only one line, while business and multiline products vary by provider and plan. 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. ISPs offer both basic and business-oriented phone services; suitability and features depend on the specific product. Basic bundled voice plans may omit advanced business features; check the specific plan for hold music, auto-attendant, ring groups, recording, voicemail-to-email and 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.
• Voice prioritisation depends on the provider and product; some NBN voice services use TC1 or other QoS mechanisms, while internet-delivered services may use best-effort data. Heavy internet use can affect best-effort VoIP when bandwidth is insufficient or voice traffic is not prioritised.
• Your number may not be portable. Local numbers are usually portable while active, but acceptance and complexity depend on the number and gaining telco, so confirm portability before relying on a new 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.

If your phone comes back but calls sound poor, crackling, echo, or dropped words, that is a separate issue with VOIP call quality on NBN. See VOIP Call Quality Guide Australia for a step-by-step diagnosis.

Your Real Options: A Proper Business Phone System

The right replacement for your old copper phone line is a cloud phone system 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
• Simultaneous-call capacity depends on the provider's licensed lines or channels as well as available network bandwidth.
• 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)

Provisioning time varies with the provider, configuration and hardware. Some providers offer rapid activation for a new number, while number porting follows a separate process.

Pricing varies by provider and may be charged per user, extension or line, with call inclusions, features, hardware and setup costs affecting the total. 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 cloud phone system 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. A disconnected number is generally placed in quarantine for six months and may be recoverable, but recovery is not guaranteed. Ask the previous telco whether it can recover or reissue the number before attempting a port.

Here is what to do right now:

• First check whether the number is active. If it is active, ask the new telco to accept and organise the port and do not cancel the old service; if it is disconnected, ask the previous telco whether it can recover or reissue it. Do not ask them to cancel, ask about porting.
• Alternatively, sign up with a new business phone company and give them your old number. They will check portability and initiate the port for you.
• Number porting generally takes 8 to 15 business days for a standard geographic number under ACMA's Local Number Portability Code. If the number has been disconnected, standard porting may not be available; recovery or reissue may be required first and is not guaranteed.
• 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 business phone companies 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. VoIP needs adequate bandwidth in both directions; upload speed is often the tighter constraint on asymmetric NBN plans. 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. Basic bundled voice plans may have limited concurrent-call capacity or business features, but capabilities and call-quality controls vary by provider and product. 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. Cancelling before the port is complete can prevent a standard port and leave recovery dependent on the telco's quarantine process, so keep the service active until the new telco confirms completion. 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 keeping the number matters, contact the relevant telcos promptly; a disconnected number is generally quarantined for six months, but recovery is not guaranteed.

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

If your phones have stopped working after an NBN migration, use our Office Phone Readiness Check to diagnose whether the problem is your connection type, router configuration, or a specific network issue, and get a prioritised fix list.

If your phones have stopped working and you are considering a full VoIP migration rather than restoring the old setup, our Phone System Switch Planner generates a realistic migration timeline and action plan based on your current situation.

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

Setup time without number porting varies by provider, system complexity, hardware and installation requirements. If you need to port your existing number from your old provider, add 8 to 15 business days for the porting process under ACMA's Local Number Portability Code. 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 the number has been disconnected, ask the previous telco promptly whether it can recover or reissue it. Recovery may be possible during quarantine but is not guaranteed, and standard porting generally requires an active number. Tell your new business phone company 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?

Cloud-phone pricing and inclusions vary by provider, plan structure, call allowance, features and hardware. Confirm whether numbers, calls, handsets, setup and advanced features are included before comparing plans. Use the Cost Calculator for a figure based on your specific situation.

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

VoIP can provide good call quality, but the result depends on bandwidth, latency, packet loss, prioritisation, equipment and provider network design. 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. You may need a different plan or service, but enhanced fault-response targets and prioritised traffic are optional features; confirm that the specific retail plan includes them and is available at your address. 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.