Conditional call forwarding, and the code for your carrier

There are two kinds of call forwarding and only one of them is any use to a plumber. Unconditional forwarding sends every call somewhere else the moment it comes in, so your phone never rings at all. Conditional forwarding leaves your phone ringing exactly as it does now, and only sends the call on when one of three things happens: you don't pick up in time, you're already on another call, or your handset is off or has no signal.

That second one is what you want. You still answer everything you can. The calls you can't answer stop going to voicemail and go somewhere that will actually do something with them.

The three conditions, and why the third one matters most

Carriers treat these as three separate switches, even where a single code sets all of them:

• No answer. Your phone rings for its usual few seconds and nobody picks up. This is the common one — you're under a sink with gloves on.
• Busy. You're already on a call. Without forwarding, the second caller gets voicemail while you're mid-conversation with the first one and never find out they rang.
• Unreachable. The handset is off, flat, or has no signal. Crawl spaces and plant rooms are full of no-signal, and this condition is handled by the network rather than by your phone, so it still fires when the phone itself is dead.

Set all three where you can. A setup that only covers "no answer" quietly stops working on the day your battery dies on a job, which is one of the days you can least afford it.

One thing to know before you look at the table: the single GSM code sets all three conditions at once, and Verizon's codes cover busy and no answer only. There is no unreachable code on that network. If you're on Verizon, the calls that arrive while your phone is off or out of signal are the ones you will still lose, and no dial code changes that.

The dial codes, by carrier

You dial these from the phone you want to forward, the same way you'd dial a number. Replace 5551234567 with the ten digits of the number you want missed calls to land on. No plus sign, no dashes, no country code.

The split is not really about the brand on your bill. It's about whose network you're on. The **004* code is part of the GSM standard, so it works across AT&T, T-Mobile and every smaller brand that rents space on them. Verizon's network doesn't take it and wants one code per condition instead. If you're on a smaller carrier that isn't listed, find out which of the big three it resells and use that row.

These codes come from public carrier documentation rather than from a phone we've tested on every network. Treat the table as a starting point and the check below as the thing that actually tells you where you stand.

How to check it worked

Dialling a forwarding code gives you almost nothing back. Some phones flash a confirmation for half a second. Some show nothing at all. Neither tells you whether the network accepted it, and this is where people get caught: they dial the code, assume it took, and find out six weeks later that it never did.

Two minutes settles it:

1. Borrow a second phone, or ask someone in the van to ring you.
2. Let it ring. Don't touch it. Wait through the full ring cycle.
3. See where it lands. If it goes to the forwarding destination, you're done. If it goes to your own voicemail, the code didn't take.
4. Then turn the phone off and ring it again, to check the unreachable condition separately. On some networks the two are set by different codes and only one of them worked.

If the call still hits your voicemail, the usual cause is the number format. Ten digits, nothing else. A leading 1, a +1, or dashes will all be accepted by the dialler and then quietly ignored by the network.

What forwarding does not do

It doesn't change your number. The number on the van, on the invoices and in every customer's phone stays the number that rings first. On the major carriers it costs nothing, because the call is being handled inside the network rather than placed a second time by you — though if you are on an older plan with a minute allowance, it is worth asking whether forwarded minutes come out of it. And it doesn't announce itself: the caller hears the same ring for the same few seconds, then whoever you forwarded to picks up.

What it also doesn't do is decide what happens next. Forwarding is plumbing, in the literal sense. It moves the call to a different place. Whether that place is another mobile, an answering service or something that texts you the details is a separate decision, and it's the one that actually determines whether the call turns into work. If nights and weekends are the gap you're trying to close, the hours are worth counting properly before you spend anything.

Turning it off

On the GSM networks, ##004# clears every conditional rule at once. On Verizon, *93 clears the no-answer rule and *91 clears the busy one, and you need both. Nothing here is permanent and nothing needs a support call to undo. That's worth knowing before you start, because what stops a lot of people trying forwarding at all is a vague sense that they'll break their phone and not be able to fix it.

The short version

Conditional forwarding is a free network setting that takes about thirty seconds to switch on and gives you a second chance at every call you can't reach. The dial code is the easy part. The part worth your attention is proving it took effect, and then having somewhere sensible for those calls to go — because a forwarded call that rings out somewhere else is the same lost job it always was. When you do get the details of one, how you ring back is what turns it into a booking.