Bad VoIP Call Quality Is Usually Your Network, Not Your Provider
What we changed on one office network to move every provider up half a point, and the order to check things in.
Bandwidth is almost never the problem
A VoIP call uses about 100 kbps in each direction. Five simultaneous calls need half a megabit. If your line is 25 Mbps or better, capacity is not why calls break up.
Jitter and buffering are
Voice packets must arrive evenly. A router that buffers heavily during a big upload will hold voice packets just long enough to make speech choppy, even though the speed test looks perfect.
The checklist, in order
- Put phones on a wired connection where you can. Wi-Fi roaming between access points drops calls more than any other single cause.
- Enable QoS on the router and give voice traffic priority. On our test network this alone lifted every provider's blind quality score.
- Turn on SIP ALG only if your provider asks for it. On most routers it corrupts signalling and should be off.
- Check for double NAT — an ISP modem in router mode behind your own router causes one-way audio.
- Separate voice onto its own VLAN once you have more than about ten phones.
- Test during a backup window. Cloud backup saturating the uplink is a classic afternoon-only fault.
When it really is the provider
If calls are poor from several networks including a mobile hotspot, if the problem follows one specific number, or if the provider's status page shows incidents, escalate. Ask for the call detail records with jitter and packet-loss figures — every provider in our ranking can produce them, and they settle the argument quickly.
» See the full rankings: Best Business Phone Systems (VoIP) of 2026, Best VoIP for Small Business, Cheapest Business VoIP Services .