The sixty-second answer
Business calls drop for four separate reasons: saturated internet upload, network loss or delay, a router timer closing the connection, or a failing forward to a cell phone. They sound identical to the caller and need different fixes. Log a week of failures before you replace any equipment.
"Our calls keep dropping" is four different problems
When a business owner says calls keep dropping, they are almost never describing one fault. They are describing a category of bad experiences that arrive through the same hole in the wall. Before anything gets replaced, split the complaint into the four things it might actually be.
The call ends by itself. Both parties were talking, and then the call was simply over. This is a genuine drop.
The call goes silent but stays connected. Nobody hung up. One side, or both, stops hearing anything. This is dead air, and it is a different fault entirely. It usually means the audio path was interrupted while the call itself remained alive.
The call never connects. The caller hears ringing that nobody in your building hears, or gets a fast busy, or lands in voicemail while three people are sitting beside idle phones. This is a routing or registration fault and it is invisible from inside the office, which is what makes it dangerous.
The call fails after being sent somewhere else. The call reached your office fine, then got forwarded to a cell phone, and died on the way. The office phone system did its job. The leg that failed was the one you cannot see.
Those four faults have almost nothing in common. Any diagnosis that does not start by separating them is guesswork.
Why voice breaks so much more visibly than everything else
Your email does not care if the network stumbles for half a second. A live phone call does, and the reason is structural rather than a matter of quality. Live voice is carried in a stream of small packets by a protocol that explicitly does not guarantee delivery, does not prevent out-of-order delivery, and does not assume the network underneath it is reliable; it numbers the packets so the receiving end can detect loss and put what did arrive back in order [1]. There is no polite second attempt. If a chunk of your sentence is lost, it is gone, because by the time it could be resent the moment for it to be heard has passed.
Delay compounds this. ITU-T guidance on one-way transmission time treats delay as something with a real upper bound, noting that a recommended one-way delay of 400 ms should not be exceeded for general network planning and that highly interactive tasks, which includes many voice calls, can be affected at lower delays than that [2]. What that means in an office is simple. Long before a call fails outright, both people start talking over each other, then start repeating themselves, then start describing the phone system as unreliable. The call did not drop. It just became unpleasant enough to feel broken.
Cause one: your upload is full
Most small business internet connections are strongly asymmetric. Download is generous, upload is not. A phone call needs upload continuously and in real time, and it is competing with everything else you send: cloud backups, security cameras uploading footage, file sync, video meetings, someone's phone backing up photos over the office Wi-Fi.
The tell is timing. If calls fail during the same window every day, or fail while the video meeting in the back room is running, you have a contention problem rather than a phone problem. This is worth measuring properly before buying more bandwidth, because in many offices the fix is prioritisation rather than capacity. We cover the numbers in bandwidth and quality of service requirements for a hosted phone system.
Cause two: the network is losing or jittering packets
Loss and jitter are the two measurements that matter, and both are reported automatically during a call by the receiving end, which estimates the variation in packet arrival times as part of ordinary reception reporting [1]. Steady loss produces clipped, robotic-sounding words. Jitter, which is packets arriving unevenly rather than not at all, produces stutter and, at the extreme, a call that abandons the audio path.
The usual sources in a small office are unglamorous: a phone on Wi-Fi that roams between access points, a cheap network switch, an aging cable run stapled along a baseboard, or a consumer router doing traffic inspection it was never sized for. Wired phones on a business-grade router fix more dropped calls than any other single change we make.
Cause three: something is timing the call out
If your calls die at almost exactly the same duration, that is a timer. Routers and firewalls expire connections they consider idle, and some phone systems and providers apply their own session limits. The call is not dropping; something is deliberately closing it.
This is the easiest fault to prove and one of the easiest to fix, but you can only see it if someone wrote down call lengths. Two or three failures at a suspiciously round number of minutes is enough evidence to stop looking anywhere else.
Cause four: the phone stopped being reachable
A phone on a modern system keeps telling the system where it is. Periodically, the device sends a registration message associating the user's address with whatever device they are currently logged into, and that binding is stored and used to route incoming calls [3]. When the binding lapses because the internet blipped, or a router restarted, or a firewall rule quietly changed, the phone still lights up and still shows the time. It just cannot be reached.
Then the call arrives, finds nowhere to land, and goes to voicemail. Everyone in the office is sitting there. Nobody's phone rang. Nothing looks broken. This is the fault most often reported as "the phone system randomly stops working", and it is why unanswered calls have to be counted as a failure mode alongside dropped ones, not treated as a separate topic. The revenue arithmetic is in what missed calls cost a Canadian small business.
Cause five: the forwarding chain
An enormous number of dropped-call complaints from small businesses come down to one habit: the office number forwards to a cell phone. When calls are forwarded from device to device, each hop is a new opportunity to fail, and the last hop is a mobile network that nobody in the arrangement controls. Worse, forwarding hides the fault. To the caller, your business dropped the call.
The alternative is not to stop using cell phones. It is to stop chaining them. A phone system can present the same business identity on a desk phone and a mobile simultaneously, ringing both, rather than passing the call down a line of forwards. That distinction is the whole subject of answering business calls on your cell phone.
The one-week diagnostic that costs nothing
Put a sheet of paper next to each phone. For every call that fails, write down: date and time; which phone; wired or Wi-Fi; caller inside or outside the building; who was speaking when it failed; and how long the call had been going. One week of that log identifies the fault most of the time, because each cause leaves a different fingerprint.
All the failures on one phone means the phone, its cable, or its jack. All the failures at the same time of day means contention. All the failures at the same call duration means a timer. All the failures on forwarded calls means the forward. Failures scattered evenly across everything means the shared network path, which is the only case where the answer is genuinely "measure the line".
Bring that log to whoever you ask for help. It also protects you commercially: if a provider tells you their service will fix your dropped calls, they are making a performance claim, and under section 74.01 of the Competition Act a performance claim must be based on an adequate and proper test, with the burden of proving that test resting on the person making the representation [5]. A log gives you something concrete to hold a promise against.
Where we sit
We run hosted phone systems for Canadian businesses, and the honest position is that we can fix some of this and not all of it. What we control is the system side: registrations that recover on their own, calls that ring your desk phone and your mobile at the same time instead of being forwarded through a chain, and a call path built on the assumption that reliable voice is an ordinary expectation for a Canadian business rather than a premium feature, which is the spirit of the policy objectives in section 7 of the Telecommunications Act [4].
What we do not control is your building's internet, your router, or the cable someone ran through a ceiling in 2011. What we will do is tell you plainly which of those is the problem, because most of the 1.08 million small businesses in Canada [6] do not have anyone on staff whose job is to know. Pricing for our hosted phone system, including how extensions are counted, is published on our pricing page rather than hidden behind a quote form.
If you are not sure your calls are dropping at all, and the real symptom is that the phone rings and nobody is free to answer it, that is a different article: start with whether a one-person business needs a phone system.