Switching your phone system to a VoIP app: the practical playbook

What a VoIP app actually replaces

A softphone app is not a feature bolted onto a phone system. For app-only businesses, it is the phone system.

A VoIP app (softphone) registers against your provider’s cloud platform over the internet, exactly as a desk phone would. Your business number, extensions, voicemail, call transfer, hunt groups and call recording all live on the provider’s platform; the app is just the endpoint. That means one migration can retire three things at once: the desk handsets, the on-premise PBX box in the server cupboard, and the fixed line rental that fed it.

The same account typically registers on several devices – a phone in a pocket, a laptop with a headset, a tablet – and rings them together or in sequence. An office number stops meaning an office desk.

When app-only works, and when you still want desk phones

App-only suits mobile, small and cost-conscious teams. A few roles still argue for hardware on the desk.

Be honest about how your team takes calls before deciding. The pattern that matters is not company size but call pattern: who is on the phone all day, who shares a handset, and who answers a main line.

The network check that decides everything

Almost every “VoIP is unreliable” story is a network story. Check capacity and quality before the first call, not after.

A single uncompressed call (the G.711 codec most platforms default to) needs roughly 100 kbps in each direction once you include packet overhead. Ten simultaneous calls therefore need about 1 Mbps of clean, consistent upstream – trivial for fibre, tight for congested wireless. Compressed codecs reduce this several-fold at a small quality cost.

Capacity is the easy half. Voice is more sensitive to consistency: one-way latency should stay under about 150 ms and jitter low, or conversations start talking over each other. If your office connection is shared with heavy downloads and video calls, ask your provider about router QoS settings that prioritise voice packets.

On the move, the app rides mobile data. At G.711 rates, an hour of calls uses roughly 40 MB – modest, but worth knowing for staff on small data bundles. WiFi-to-LTE handover mid-call is also the classic drop point; staff who roam should know a moving call may re-establish.

Choosing the provider for an app-first setup

The questions are slightly different when the app is the whole phone system, not an add-on.

Beyond the standard diligence – licence, SLA, reviews, contract terms, which we cover in our provider trust checklist and selection guide – press on four app-specific points:

Platform coverage. The app must be first-class on iOS, Android, Windows and macOS, because your team is on all four. Ask to see the app working in the demo, not a screenshot.

Multi-device behaviour. Can one extension register on a phone and a laptop at once, and ring both? How does it handle the handover when you leave the office mid-call?

Per-user pricing. App-first plans are usually priced per user or extension per month. Get the rate card in writing, including call rates, and confirm what happens to the price when you add or remove users.

Porting process. The provider will move your existing number through the regulated porting process. Confirm timelines and, critically, the sequencing: the old service stays live until the port completes.

The switch, in five steps

The order is the point. Most failed migrations skipped a step or ran them backwards.

The problems you will actually hit, and the fixes

Four issues account for nearly all app-migration complaints. All four are preventable.

Calls drop when moving between WiFi and mobile data. This is network handover, not the app failing. Staff who roam during calls should prefer one network for the duration, or expect a brief re-registration.

Android stops ringing in the background. Aggressive battery optimisation can suspend the app. The fix is one-time: exclude the VoIP app from battery optimisation in the phone’s settings, and confirm push notifications for incoming calls are enabled.

Audio quality dips at busy times. Usually congestion on the office connection. Enable QoS for voice on the router, or move call-heavy users to the wired network.

The team quietly reverts to cellphone numbers. The costliest failure, because your business number stops being the front door. It is a training and habit problem: make the app the default dialler for work calls, and make sure outbound calls present the business number.

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