Here is the short answer. Today, business phones usually run over the internet, so when the connection drops, the phones stop too. The good news is that you can keep calls flowing with a few simple backups, and good internet for business is built to fail less often in the first place. Sixfam sets up business phones and internet for companies across Melbourne and regional Victoria from its base in Keysborough, so this is the exact problem we plan around every day.
Internet phones stop because the calls travel over your internet line. These days, business phones usually run as VoIP phones. VoIP means Voice over Internet Protocol. In plain terms, your calls go over the same connection as your email and web browsing, not over an old copper phone line. That brings real benefits. It costs less, it is easy to add lines, and you can take your number with you. The trade-off is simple. No internet, no calls. When the line drops, the phones have no path to send or receive a call, so they go silent until the connection comes back.
This happens the instant the line drops. A call already in progress cuts out, and new calls can’t get through at all. There is no slow warning, so the first sign is often a customer telling you later that they couldn’t reach you.
A power cut does the same thing for a different reason. Your modem, router and network switches all need power to run. If they lose it, the phones go down even when the internet line itself is fine. So there are two things to plan for: losing the line, and losing power.
| Option | How it works | Rough cost | Best for |
|---|---|---|---|
| Automatic call divert to mobiles | Incoming calls reroute to staff mobiles when the system can’t be reached. Set once in the phone system. | Usually included or low cost | Every business. The simplest safety net. |
| 4G or 5G backup connection | A mobile SIM in your router takes over in seconds when the fixed line drops, then hands back when it returns. | Small monthly add-on | Offices that need data and calls to stay up, not just calls. |
| Second (redundant) internet service | A separate connection on a different network runs as a spare path if the main one fails. | Cost of a second plan | Where an hour offline is expensive, such as clinics or sales teams. |
| SIP-level redundancy | Your provider reroutes calls inside the network before they reach your office. SIP is the signalling that sets up VoIP calls. | Often part of a hosted plan | Businesses that can’t miss a call, even briefly. |
Many offices start with automatic divert and add a 4G backup. That pairing keeps the phones answered for a low monthly cost. A 4G backup runs slower than your main line, often set around 25/5 Mbps, so it is there to keep you working, not to feel the same as full speed. Sixfam runs these on monthly billing with no lock-in contracts, so you can add a backup for a busy season and review it later.
Business NBN and consumer NBN can run on the same wires, but they are not the same product. The difference is in what happens when something breaks, and how fast you get help. That is why nbn business plans cost more than a home plan. You are paying for the promise, not just the speed.
The first difference is the SLA. An SLA is a Service Level Agreement, a written promise about response and repair times. On business fibre you can choose an enhanced fault response window, often 4, 8 or 12 hours, where a home plan offers no such promise and a fault simply waits its turn. Faults on business services are also treated as higher priority, so help arrives sooner.
The second difference is the type of connection. Enterprise Ethernet is a business-grade option that uses a dedicated fibre line just for you. It runs at matching upload and download speeds, from 10/10 Mbps up to 1000/1000 Mbps. Matching upload speed matters for calls, because VoIP sends voice out as well as in. A home plan usually gives you far less upload than download.
The third difference is the small print that keeps phones working. Business plans usually offer a static IP, which is a fixed internet address that does not change. Some phone and security setups need one. “Business grade” is more than a label. It is the repair promise, the priority, and the steadier connection underneath.
Sometimes it helps, and sometimes it makes no real difference. Here is the honest version. The clearest benefit is fault resolution. Fault resolution just means getting the problem fixed and your service back. When your phones and internet come from one provider, there is one number to call. No one can say the fault belongs to the other provider while your calls stay down. One team sees the connection and the phone system together, so they often find the cause faster.
Sixfam has run this way for 15+ years and supports around 600 business customers on monthly billing. Support is Australian and local. For faults a remote fix can’t solve, a technician can come on site across south-east Melbourne and regional Victoria. A cut fibre line or a hardware failure sometimes needs a person on the ground, not just a call to a support queue. If you run a business phone system in Melbourne, the connection under it matters as much as the handsets.
Being honest, the same-provider setup is not magic. If your office is small and your connection rarely drops, two reliable providers work fine, and there is no need to switch just to bring everything under one roof. The case for one provider is strongest when your phones are business-critical and you want a single point of accountability when something goes wrong. Sixfam offers phones, internet and mobile together, but the reason to take all three is accountability. A bundle discount is not the point.
The fastest way to know where you stand is to test it, not assume it. Pick a quiet moment and unplug the internet at your router for two minutes. Watch what happens to an incoming call to your main number. If it reaches a mobile or a voicemail, you have some cover. If it rings out into silence, you do not.
There is one question worth asking your current provider too: “If my internet drops right now, where does a call to my main number go?” Many businesses assume they have failover when all they have is a number that rings out. The answer to that one question tells you in a sentence.
If you would rather not guess, Sixfam can run a continuity check on your current setup: what diverts, what does not, and how long until a call reaches a real person. Call 03 9200 2800 to book one.
VoIP phones stop working in a power cut unless you have battery backup. Your modem, router and switches lose power, so calls have no path. A battery backup unit, called a UPS, keeps that gear running for a while. Automatic call divert to mobiles is the simpler fix, because it reroutes calls away from the dead equipment.
Yes. Automatic call divert sends incoming calls to a mobile when your phone system can’t be reached. It is set up once in the system and then runs on its own. It is the cheapest safety net and the first one to turn on.
A 4G backup is a mobile connection that takes over when your fixed line fails. A SIM sits in your router and switches over in seconds, then hands back when the line returns. It runs slower than your main connection, often around 25/5 Mbps, so it keeps you working rather than matching full speed.
Business NBN is worth it when downtime costs you money. It adds faster fault response and, on some plans, a written repair-time promise that a home plan does not include. If your phones and card payments run on the connection, that promise is the point.
An SLA is a Service Level Agreement, a written promise about response and repair times. On business plans it can include an enhanced fault response window, sometimes 4, 8 or 12 hours. A consumer plan gives you no such promise, so a fault waits its turn.
It depends on the cause and your plan. A setting or system fault can be fixed remotely in minutes. A cut line or hardware failure may need a technician on site, which is where local support and a repair-time SLA matter most.
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