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Dropped VoIP Calls: Causes, Checks and Fixes for Businesses

Dropped VoIP Calls: Causes, Checks and Fixes for Businesses

28 October 2026

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Dropped VoIP Calls: Causes, Checks and Fixes for Businesses

Employee checking desk phone after dropped call

VoIP calls usually drop for one of four reasons: an unstable or congested internet connection, Wi-Fi between the handset and the router, a router or firewall setting that closes the call, or a fault at the VoIP provider. The pattern of the drops tells you which. Calls that die at random, with choppy audio first, point to the network. Calls that die at the same moment every time point to a timer or a setting. This guide shows you how to tell them apart and what to do about each.

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TL;DR

  • Note when calls drop: random drops with robotic audio suggest packet loss or congestion; drops after a fixed time suggest a router, firewall or session timer setting.
  • Plug desk phones and computers into the router with Ethernet cable before you blame the provider. Wi-Fi is the most common weak link.
  • Prioritise voice traffic on the router and keep large uploads and backups away from call hours.
  • If the fault survives a wired test on a quiet network, log call times and numbers and take them to your provider, and check your contract’s service-level agreement.
  • Repeated drops on a shared, contended line are often a sign that you need a different connection, not a different phone system.

Table of Contents

What a dropped VoIP call actually is

A VoIP call is a stream of small data packets travelling in both directions, many times a second. The call survives only while those packets arrive quickly and in order. Two measurements matter most:

  • Packet loss: packets that never arrive. A little causes clipped words. A lot ends the call.
  • Latency and jitter: latency is the delay between sending a packet and it arriving; jitter is how much that delay varies. High jitter makes the voice stutter, and the system may give up on the call.

A second thing can also end a call: the signalling layer. VoIP uses a separate conversation (usually SIP) to set up and keep the call alive. If a router or firewall blocks or times out that conversation, the call ends even though the audio was fine a second earlier.

That split is the key to diagnosis. Audio problems build up before a drop. Signalling problems tend to cut a call dead, often at a repeating interval.

Work out the pattern first

Before touching any settings, spend two or three working days writing things down. A shared spreadsheet is enough. For every dropped call, record:

  • the date and time
  • the extension or handset, and whether it was wired or on Wi-Fi
  • who was on the other end (internal, mobile, landline, a particular customer)
  • how long the call had lasted
  • what the audio was like in the minute before
  • what else was happening on the network (a large upload, a video meeting, a software update)

Then read the notes against this table.

What you see Most likely cause First thing to try
Choppy, robotic audio, then a drop, at busy times Congestion or packet loss on your line Test at a quiet time; prioritise voice; check bandwidth
Drops only on Wi-Fi handsets or softphones Wi-Fi interference or weak signal Move to a wired connection
Drops at a fixed interval (30 seconds, a few minutes, hours) Router, firewall or session timeout Check NAT, SIP ALG and keepalive settings
Drops only to one network or one number Fault with the other party or an interconnect Report to your provider with examples
Every device drops together, internet also slow Broadband fault or overloaded line Run a line test; contact your internet provider
One handset only Faulty handset, cable or port Swap the handset and cable

This is a starting point, not a verdict. But it saves hours of changing things at random.

Check the internet connection

Most dropped calls trace back to the connection. Voice needs very little bandwidth per call, but it needs that bandwidth to be steady.

Latency, loss and jitter

Cloud contact-centre documentation gives a useful benchmark. Amazon Connect’s network troubleshooting guide says average latency in its endpoint test should not exceed 300 ms, and it links Wi-Fi interference and congestion to jitter and packet loss. The same vendor’s guidance on call quality metrics explains that high packet loss suggests a poor or congested path, and high jitter-buffer delay suggests congestion or low bandwidth. High round-trip time, it adds, can be associated with constrained networks, VPNs or distance from the service.

VoIP latency packet loss and jitter measures

You do not need to be an engineer to use that. Run a continuous ping to your router and then to a public address while a call is in progress, or ask your provider for a line test. Steady, low numbers with an occasional spike point you towards a congested moment. Lost pings point to the line or the equipment.

Is the line shared or contended?

Standard business broadband is shared with other users on the same network. In the evening that matters less for offices, but a busy office making many simultaneous calls while staff stream video, sync cloud files and join video meetings can saturate the upload side first. Upload is the usual bottleneck, because broadband is typically weaker in that direction and voice needs steady upload.

Symptoms of an overloaded upload: your callers hear you break up while you hear them perfectly, and the drops line up with someone sending a large file.

Options, in order of cost:

  1. Schedule backups and large uploads outside call hours.
  2. Prioritise voice traffic on the router (see below).
  3. Upgrade the connection. Fibre broadband gives more headroom; a leased line gives a dedicated, symmetrical connection with a guaranteed service level, which is why busy offices running many concurrent calls often choose one.

Add a backup line

If a line fault is the cause, no setting will fix it. A 4G or 5G router that takes over automatically when the main line fails keeps calls alive, or at least lets them resume within seconds. For a small office whose phones are its income, that is often the cheapest insurance available.

Take Wi-Fi out of the equation

If the drops cluster on laptops with softphones, Wi-Fi handsets or phones in a far corner, test with a cable. Amazon Connect’s guidance is direct: it recommends fixed Ethernet over Wi-Fi, and keeping large transfers off the same Wi-Fi environment as your calls.

Wi-Fi drops calls for ordinary reasons:

  • walls, floors and metal fittings weaken the signal
  • neighbouring offices’ networks use the same channels
  • too many devices share one access point
  • a handset roams between access points and loses a few seconds of audio

A quick test: plug the affected device into the router with a short Ethernet cable and make the same calls for a day. If the drops stop, it was the wireless link.

Then fix it properly rather than leaving a cable trailing across the floor. A wifi survey and design maps signal strength and interference across the premises and places access points where they are needed. Where desk phones and fixed PCs are the problem, professional network cabling gives each desk a wired port, which removes the wireless link entirely. Old or damaged cabling, poor terminations and overlong runs can also cause intermittent faults that look like provider problems, so it is worth testing the cable before blaming anything else.

Router, firewall and settings that end calls

When calls drop at the same point every time, think timers. The common culprits:

  • NAT timeouts. Your router keeps a temporary record of each outgoing connection. If it expires that record while a call is quiet, returning packets are discarded and the call goes silent or ends. The remedy is usually a keepalive setting on the phone system or handset, or a longer timeout on the firewall.
  • SIP ALG. Some routers include a feature that rewrites SIP traffic. On many setups it does more harm than good, causing one-way audio and dropped calls. Disabling it is a standard first step, but check your provider’s guidance for your router.
  • Session timers. SIP can refresh a call at intervals to confirm it is still alive. If the refresh is blocked or mishandled, the call ends at a regular interval.
  • Firewall rules, proxies and VPNs. Amazon Connect’s guidance lists firewall, proxy, VPN and NAT problems as causes of audio issues, drops and delays. A VPN that sends voice over a long detour adds latency and loss.
  • Router congestion. The same guidance recommends increasing bandwidth or replacing the router if it cannot cope with the traffic.

Calls dropping after a set time

People often ask why calls drop after exactly the same period, such as eight hours. A fixed interval is almost never random. It usually means a timer somewhere: a session timer on the phone system, a connection timeout on the firewall, or a lease renewal on the router (for example, a DHCP lease or a reconnect schedule that interrupts live traffic). The note you made about call length is what identifies it. Compare the interval with the timeouts configured on the router, the firewall and the phone system, and change the one that matches. If you cannot see those settings, your provider can read them from the call logs.

Prioritise voice with QoS

Quality of service (QoS) tells the router to treat voice packets as urgent. When the line is busy, ordinary data waits and voice goes first. Cisco’s troubleshooting guide recommends a queuing technique that identifies and prioritises VoIP traffic, because dropped packets and bottlenecks cause delay and jitter. For a deeper look at how quality of service settings queue and mark traffic, that guide walks through the principles.

Two practical points:

  • QoS only controls traffic on equipment you manage. It helps on your own network and at your router’s outbound queue, which is where most office congestion happens. It cannot fix a faulty line or congestion elsewhere on the internet.
  • It works best when the phones, the switch and the router all agree on the markings. Mixed equipment with default settings often means QoS is switched on in one place and ignored in another.

A step-by-step checklist

Work through this in order. Stop when the problem stops.

  1. Log the drops for two to three working days, using the fields above.
  2. Reboot the router, switch and handsets once, then see whether the pattern changes. A faulty device often misbehaves for days before it fails.
  3. Go wired. Move affected handsets and computers onto Ethernet.
  4. Test at a quiet time. If calls are fine at 7 am and poor at 11 am, you have a capacity problem.
  5. Pause heavy traffic. Stop backups, updates and cloud syncs for a morning.
  6. Check the router. Look at SIP ALG, NAT timeout and firmware version. Update firmware if it is out of date.
  7. Turn on voice prioritisation across router and switch.
  8. Run a line test with your broadband provider and look at error counts and speed stability.
  9. Escalate to your VoIP provider with call logs if only certain calls or destinations are affected.

Change one thing at a time. If you change four settings at once and the problem disappears, you will not know which one mattered, and you will not know what to do when it returns.

When to contact your provider

Some faults are not yours to fix. Contact your broadband or VoIP provider when:

  • the problem persists on a wired, quiet network
  • only calls to or from specific numbers or networks fail
  • several devices on different networks drop calls at the same time (which suggests a platform issue)
  • your line test shows errors or unstable sync
  • the fault has repeated despite earlier fixes

Give them the evidence: the log of times, extensions and destination numbers, what you have already tried, and the router and handset models. A provider can trace a specific call in minutes if it has a timestamp and a number. “Calls keep dropping” can take days.

Check your contract at this point. Ofcom says a business contract may include a service-level agreement covering fault-repair times, support response, connection speed and the maximum days without service. If faults keep recurring and affect your operations, that document tells you what you are entitled to ask for.

Also treat one kind of failure as urgent. In September 2025 Ofcom fined a VoIP provider £700,000 after a software update left some UK business customers unable to call emergency services from desk phones. If you ever suspect that your phones cannot reach 999 or 112, tell your provider immediately, and keep a mobile available as a fallback until it is confirmed fixed. Do not wait for the next routine call to test it.

Our perspective on dropped calls

We see the same pattern across Essex and London offices. A business reports that “the phone system is rubbish”, and when we look, the system is fine. The cause is a cheap router that nobody has touched in years, a handful of handsets on a weak Wi-Fi signal, or a single contended line carrying phones, cloud backups and video meetings at once.

Three things we would tell any office manager:

  1. Fix the network before you change the phones. Switching VoIP provider without fixing the line usually moves the problem to a new logo. Wired desks, a router that can prioritise voice and a connection sized for the number of concurrent calls solve most cases.
  2. Plan for failure. Lines do fail. A 4G or 5G backup router, or a second route, turns an outage into a short blip. If calls are how you earn, that is not a luxury.
  3. Ask for evidence, not reassurance. Any supplier, including us, should be able to show you call logs and line tests that explain a fault. We offer UK-based support and flexible terms without long-term lock-in, so you are never held to a service that is not working.

We are also vendor independent, which means we can look at the connection, the cabling and the phone system as one problem instead of defending one product.

— Paul

How we can help

If you have worked through the checklist and calls still drop, the cause is probably in the connection or the cabling, and that is where we can step in.

Tell us when the drops happen and what equipment you have, and we will tell you where we think the fault sits.

FAQ

Why are my VoIP calls dropping?

The usual causes are packet loss or congestion on the internet line, a weak Wi-Fi link, a router or firewall setting that times out the call, or a fault at the provider. Note when the drops happen, and whether they affect wired and wireless devices alike, and the likely cause usually becomes clear.

Why do calls drop after a fixed length of time?

A repeating interval points to a timer rather than a poor line. Common candidates are a NAT or firewall timeout, a SIP session timer, or a router reconnect or lease renewal. Compare the call length with the timeouts set on your router, firewall and phone system, and adjust the one that matches.

Can Wi-Fi cause dropped VoIP calls?

Yes. Interference, distance, walls and too many connected devices all cause the packet loss and jitter that end calls. Amazon Connect’s guidance recommends fixed Ethernet over Wi-Fi where possible. If you must use wireless handsets, a proper wifi survey places access points where the coverage is needed.

Do I need a leased line to stop dropped calls?

Not always. Many small offices are fine on fibre broadband with a good router and voice prioritisation. A leased line makes sense when you run many simultaneous calls, rely on cloud systems all day, or cannot tolerate a contended connection.

What should I send my provider when calls keep dropping?

Send a log of dates, times, extensions and destination numbers, the length of each call before it dropped, what you have already tried, and your router and handset models. Specific timestamps let a provider trace individual calls instead of guessing.

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