What actually changes when you move off a landline to VoIP

VoIP means your calls travel over your internet connection instead of a copper pair, which turns the phone system from a box on the wall into software. Software can do things the box never could: ring your mobile and your desk at once, follow you to a laptop at home, and add a person in two minutes rather than an engineer visit.

The trade is that your phones now depend on your internet connection and on how your network is set up. On the old line, call quality was somebody else's problem. Now a chunk of it is yours, and nobody explains that at the point of sale.

One thing on timing. Openreach is retiring the old analogue network and the deadline has already moved more than once, so do not plan around a date you read in an article, including this one. Ask your provider what applies to your lines, and get it in writing.

Most of the change is straightforwardly good, and it arrives immediately rather than gradually.

Porting is moving a number you already own from one network to another. It is a regulated handover between two providers, scheduled to a moment, and it is the part that goes wrong.

It matters more than anything else in the project, because for most businesses the main number is on the vans, the website, the letterhead and in every existing customer's phone. Calls to it during a botched port do not reach a holding message. They fail, and the caller assumes you have gone out of business or rings the next name on their list. You never find out how many.

The way to keep this dull is to get the order right. The new system should be built, configured and tested before the number moves, so when it lands it arrives on something that already works. The reverse order, where the number ports first and the routing is assembled around it afterwards, is how firms end up with a live main number pointing at a half finished setup on a Tuesday morning.

Three practical points save most of the grief. Check your account details match exactly what the losing provider holds, because a mismatch in the company name or installation address is the most common cause of a rejected port. Never cancel the old service yourself, because doing so before the port completes can destroy the number. And expect weeks rather than days.

Call quality problems on VoIP rarely look like a slow line. They show up as specific symptoms, each pointing at a different cause.

Choppy audio, where words drop out, is usually packet loss: pieces of the call are not arriving. Robotic or underwater audio is usually jitter, where the pieces arrive at uneven intervals and the phone guesses how to reassemble them. Long gaps where you talk over each other are latency. One way audio, where you can hear them and they cannot hear you, is almost always a firewall or router configuration problem rather than a line problem at all.

The common causes are unglamorous. A line that is fine at eight in the morning and struggling at half past eleven when everyone is on video calls. A consumer router that cannot prioritise voice traffic when the connection is busy. Handsets on wifi in a building where the wifi was never designed properly, which is a common cause of complaints. Or a firewall doing something clever with call setup traffic that breaks the audio in one direction.

The rule worth remembering: voice needs very little bandwidth but it is fussy about consistency. It is happier on a modest line that behaves predictably than on a fast line that stutters.

The platform matters less than most people expect. Which calls get answered comes down to the routing, and that is the part that gets rushed because everyone is focused on the handsets arriving.

Spend an hour on it before go live. Where does a call go first, and for how long before it moves on? Who picks up if that person does not? What happens between five and nine in the morning, at lunchtime, on a Saturday, and on the bank holiday nobody remembered to configure? Does the caller reach a queue, a mobile, a voicemail somebody monitors, or a ring that goes nowhere?

Two settings do most of the damage. A ring time so long that callers hang up before the call moves on, and a menu with too many options read too slowly, so people press zero or give up. Both are easy to fix and both quietly cost you calls until somebody looks.

Run this list before the port date, not after. Nearly everything on it can be checked in an afternoon, and each item catches a problem that is much more expensive to find later.

The phones are rarely the only thing on the old line. Each of the following is worth checking, because each has stopped somebody's system on cutover day.

VoIP is a better phone system than the one it replaces, and two things decide whether it feels that way: the connection underneath it, and the care taken over the port. Neither is expensive to get right. Both are painful to fix afterwards.

If you are being pushed to switch and are not sure your line will carry it, that is a testable question rather than a matter of opinion. We can monitor the connection for a fortnight and tell you plainly whether the phones will be fine, whether the wifi needs sorting first, or whether you need a better line first.