Why Are My VoIP Calls Breaking Up? Common Causes and Fixes

Choppy or breaking-up VoIP calls are almost always down to something happening on your network, not a fault with the phone system itself. The most common causes are a Wi-Fi connection instead of a wired one, other devices competing for bandwidth, no Quality of Service (QoS) prioritisation set up, or a VPN running in the background. Working through these in order usually finds the cause without needing to call anyone.

Is It Happening on Every Call, or Just Some?

This is worth establishing first, since it points to a different type of problem:

• Every call, for everyone — usually a network-wide issue, such as bandwidth, QoS, or an ISP problem
• Only for one person — usually something local to that person's device, connection, or headset
• Only at certain times of day — usually network congestion during your business's busiest hours

Common Cause 1: Wi-Fi Instead of a Wired Connection

Wi-Fi is more prone to interference, signal drop-off, and congestion than a wired connection, all of which show up as choppy audio on a call. If a desk phone or softphone is connecting over Wi-Fi rather than an ethernet cable, this is often the simplest thing to fix first.

Fix: Where possible, connect phones and any computer used for calling directly to the router or network switch with a cable, particularly for anyone taking calls regularly throughout the day.

Common Cause 2: Network Congestion from Other Devices

Large file uploads, video streaming, cloud backups, or several people on video calls at once can all eat into the bandwidth your phone calls need, especially if nothing's prioritising voice traffic over everything else.

Fix: Check what else is running on your network during problem calls. If it's a recurring pattern — for example, calls breaking up whenever a colleague uploads large files — that's a strong clue you've found the cause.

Common Cause 3: No Quality of Service (QoS) Configured

Without QoS settings on your router, voice traffic gets treated the same as everything else, meaning a large download can delay your call's data packets without your router knowing voice should take priority.

Fix: Configure QoS on your router or firewall to prioritise voice traffic. Our guide to optimising QoS for VoIP walks through this in more detail.

Common Cause 4: A VPN Running in the Background

VPNs route all your traffic through an external server, which adds distance and processing overhead. This can introduce exactly the kind of delay and packet loss that causes choppy calls, even on an otherwise good connection.

Fix: If calls consistently sound worse with a VPN active, try a call with it switched off to confirm. Some VoIP systems support routing voice traffic outside the VPN specifically, which is worth asking about if VPN use is unavoidable for other reasons.

Common Cause 5: Router or Firewall Issues

An older, underpowered, or misconfigured router can struggle to handle VoIP traffic properly, and some firewall settings interfere with how voice data packets are handled, causing dropped or choppy audio.

Fix: Check your router isn't out of date or overloaded, and confirm your VoIP system's required ports aren't being blocked or throttled by a firewall. This is often something a specialist needs to check rather than something obvious from the router's settings page.

Common Cause 6: An ISP-Side Problem

Sometimes the issue isn't your network at all — it's happening further upstream, on your internet provider's side, particularly during known outages or local network issues.

Fix: Check whether the problem affects general internet use too, not just calls. If browsing and other online activity are also sluggish, it's worth contacting your ISP directly rather than assuming the phone system is at fault.

Common Cause 7: Headset or Hardware Fault

If the problem's isolated to one person, a faulty headset, damaged cable, or an ageing handset can sometimes be the actual cause, rather than anything network-related at all.

Fix: Try the same call with different hardware — a different headset, or calling from a mobile app instead of the usual device — to rule this out quickly.

How to Test What's Actually Going Wrong

1. Note whether the issue affects everyone or just one person, and whether it's constant or occasional.
2. Try a call over a wired connection instead of Wi-Fi, if not already using one.
3. Check what else is running on the network at the time calls break up.
4. Try the same call with any VPN switched off.
5. If the problem persists across all of the above, it's worth getting your network properly assessed rather than continuing to guess.

Frequently Asked Questions

Can slow broadband alone cause calls to break up? Yes, but it's often not simply about overall speed — insufficient upload bandwidth or a lack of prioritisation for voice traffic causes more call quality issues than raw download speed alone. Our guide to VoIP bandwidth requirements explains what to check.

Why do my calls only break up at certain times of day? This usually points to network congestion during your busiest hours, when more devices and traffic compete for the same bandwidth.

Does a mobile app version of my phone system have the same issue? Not necessarily. If calls are fine on a mobile app using mobile data but poor on the office Wi-Fi, that's a strong sign the problem sits with your office network rather than the phone system itself.

When should I stop troubleshooting and just ask for help? If you've worked through the network and hardware checks above and the problem's still happening, it's a good sign the issue needs a proper network assessment rather than more guesswork.

Persistent call quality problems are almost always fixable once the actual cause is identified. Request a quote if you'd like T2K to assess your network properly, or read our guide to VoIP bandwidth requirements if you're planning a new system from scratch.