Your phone number is painted on the van, printed on the menus, saved in hundreds of customers' phones and listed on your Google profile. Changing it isn't on the table. The good news is that you don't have to. Call forwarding to AI receptionist services works with the number you already have: customers ring the same number as always, and your phone provider quietly passes the call on.
This article explains how that works in practice, the four kinds of forwarding and when to use each, the codes for the main UK and US carriers (with links to their own help pages, because codes change), and how to test the whole thing before a real customer depends on it.
How call forwarding to AI receptionist numbers works
When someone rings your number, the call reaches your phone provider first. Normally the provider rings your phone. With forwarding switched on, the provider sends the call to a different number instead, either straight away or only in certain conditions.
From the caller's side, nothing changes. They dial your number and someone (or something) answers. They don't hear a second dial tone or a message saying they're being transferred.
Two details matter for cost and reliability:
- There are two legs to every forwarded call. The first is the customer's call to you, which they pay for as normal. The second is the call your provider makes from your number to the forwarding destination. Many providers charge you for that second leg, as if you'd made the call yourself.
- Forwarding is set on your line, not on the AI's. The AI receptionist can't switch it on for you. You (or whoever manages your phones) set it with your provider, using dial codes, a phone setting or an online account.
How forwarding works with Klugon
Every service does this slightly differently, so here's Klugon as one example.
Three ways to connect a number
In the assistant's Voice tab, under Phone number, there are three options:
- Buy a number. Klugon gets you a new number, and callers dial that. Useful for a new business or a separate line, but you'd need to publish the new number.
- Forwarding. Klugon gives you a dedicated number, and you set your existing number to forward calls to it. This is the "keep your number" option, and the one this article is about.
- Bring your own. If you run your own SIP trunk (common with larger business phone systems), you point it at Klugon's server. This needs a voice plan on the Business tier or above.
Number porting, moving your actual number over to Klugon, isn't supported. Forwarding or a SIP trunk is how you keep your number.
What the forwarding number costs and when you can get it
The dedicated number costs $9 a month, on top of a voice plan. Voice plans start at $99 a month with 1,000 minutes; the pricing page has the full table, including how many numbers each tier allows (one on Starter, three on Business, unlimited on Scale).
There's a 7-day trial, and a card is required. During the trial you can test the assistant in your browser, but phone numbers only activate once the trial has ended. So the order of events is: set up and test in the browser during the trial, then add the forwarding number, then switch on forwarding at your provider.
Choose a number in the same country as yours
When you pick the forwarding number, you choose a country and, optionally, an area code. Pick the same country as the number you're forwarding from. Several carriers don't allow forwarding to international numbers at all: Verizon and AT&T both say so on their own help pages, linked below. Even where it's allowed, a forwarded call abroad can cost far more.
One assistant per number, answering whenever a call arrives
Each phone number is assigned to one assistant, and you can move it to a different one from the same panel. The assistant answers any call that reaches its number, at any hour. There's no setting inside Klugon that stops it answering outside your opening hours, so if you only want it to answer at certain times, you control that with forwarding: switch it on at closing time, or use a time-based rule on your phone system.
It's worth knowing what happens on the call, too. The assistant can answer from your knowledge base, check free slots and book or cancel appointments, and save the caller's details as a lead. It can't put a caller through to you; when someone needs a person, it saves their details with a note and flags the conversation for your team, and on a voice Business plan or above it can notify Slack or Zapier. More on that is on the AI phone receptionist page.
The four types of call forwarding
Most landlines and mobiles support four forwarding conditions. Choosing the right one is the most important decision in this setup.
| Type | What happens | Best for |
|---|---|---|
| All calls (unconditional) | Every call goes straight to the AI. Your phone doesn't ring. | Out of hours, or if you're never free to answer during the day |
| Busy | If you're on a call, the next caller goes to the AI instead of an engaged tone or voicemail | Catching the second caller when you're already talking |
| No answer | Your phone rings for a set time, then the call goes to the AI | Keeping every call you can take, and catching the rest |
| Unreachable | If your mobile is off or has no signal, calls go to the AI | Mobiles used on site, in basements or in poor coverage |
Three common setups
Most businesses use one of these combinations:
- Busy + no answer + unreachable during the day, all calls at night. You answer when you can; the AI catches what you miss; out of hours it takes everything. This is the most common setup for owner-operators.
- All calls, all the time. The AI answers every call and flags anything that needs a person. Suits businesses where nobody is ever free to answer, or where most calls are bookings and routine questions.
- All calls, only after hours. You keep the phone during opening hours, and forward everything when you close. A gentle way to start. Our after-hours answering service page covers this setup in more detail.
Setting the no-answer ring time
With no-answer forwarding, the ring time matters. Too short and you can't reach the phone; too long and callers give up before the AI answers. BT's landline divert uses a fixed 15 seconds. Many mobile networks let you choose, usually in steps of five seconds. Fifteen to twenty seconds suits most businesses.
Watch out for your own voicemail. If your mobile's voicemail picks up after 15 seconds and your no-answer forward is set to 20, voicemail wins every time.
UK carrier codes for call forwarding
In the UK, forwarding is usually called call diversion. Codes differ between landlines and mobiles, and between providers, so use the links to check the current codes for your own line.
BT landlines
BT lists these codes on its call diversion help page. Dial them from the line you want to divert, using a phone set to tone dialling:
| Divert | Set up | Cancel |
|---|---|---|
| All calls | *21* then the number then # | #21# |
| Not answered within 15 seconds | *61* then the number then # | #61# |
| When busy | *67* then the number then # | #67# |
On BT Digital Voice, you can also set diversion from a compatible handset's menu. BT's page says Call Diversion is included for Digital Voice customers, but that diverted calls are charged at your normal rate for the call duration plus a set-up fee unless they're covered by your package, and that diverting to a mobile costs more than to a landline. If you're diverting to a geographic or standard UK number, check whether your inclusive minutes cover it.
Vodafone mobiles
Vodafone's help page on managing call diverts gives the codes for its mobiles. Replace the first 0 of the destination number with +44.
| Divert | Set up | Cancel |
|---|---|---|
| All calls | **21* then the number then # | ##21# |
| Unanswered calls | **61* then the number then # | ##61# |
| When busy | **67* then the number then # | ##67# |
| Cancel every divert | ##002# |
To change the ring time before an unanswered call is diverted, Vodafone's page gives **61* then the number, then *10*, then the number of seconds, then #.
One important limit: the same page says that on Pay as you go, incoming calls can only be diverted to voicemail. If your business mobile is PAYG, you may need to move to a monthly plan before forwarding to an AI receptionist will work.
EE, O2, Three and other networks
Most UK mobile networks use the same standard GSM code family as Vodafone (**21*, **61*, **67*, **62* for unreachable, and ##002# to cancel everything), but they don't all allow every divert on every plan or to every kind of number. Check your network's own help pages or ask customer services before relying on a code you found elsewhere. You can usually check what's set by dialling *#21#, *#61# or *#67#.
US carrier codes for call forwarding
US carriers vary more than UK ones, and some only let you change forwarding from the phone itself.
Verizon
Verizon's call forwarding guide gives these codes for its mobile service:
| Forwarding | Code |
|---|---|
| All calls | *72 then the number |
| Only when busy or not answered | *71 then the number |
| Turn off forwarding | *73 |
Verizon's page also says you can't forward to an international number, that there's no monthly fee for call forwarding on current plans, and that airtime charges apply to all forwarded calls. Verizon business and home phone products can use different codes, so check the guide for your product.
AT&T
AT&T's call forwarding for wireless page says you can only change forwarding settings from the phone itself, not online. On most phones, that's under the Phone app's settings, then Call forwarding. The page also notes that forwarding overrides your wireless voicemail, that you can't forward to an international number, and that forwarded calls are billed for their full length.
T-Mobile and other networks
T-Mobile and other GSM-based networks generally accept the standard codes (**21*, **61*, **67*, **62*, ##002#), and most phones also have a Call forwarding menu in their settings. As with every carrier, check your own carrier's support pages, especially if you're on a business plan.
Business phone systems and VoIP
If you use a cloud phone system rather than a plain landline or mobile, you probably won't use star codes at all. Look for the routing, call flow or forwarding settings in the admin panel. These systems usually give you more control than a mobile:
- Time-based rules. Ring the office during opening hours, forward to the AI receptionist outside them, automatically. This solves the "no business-hours setting" point above without anyone remembering to switch forwarding on at closing time.
- Ring groups with overflow. Ring several phones first; send the call to the AI if nobody picks up.
If your system supports SIP trunks, you might prefer Klugon's bring-your-own option on the Business tier instead of forwarding, but for most small businesses forwarding is simpler.
Step-by-step setup checklist
Here's the whole process in order.
- Set up and test the assistant first. Add your hours, services and common questions, and talk to it in the browser until you're happy with its answers. Our guide on how to train an AI receptionist covers what to add.
- Write the call greeting. It's what every forwarded caller hears first, so make sure it names your business. See our business phone greeting examples.
- Decide which forwarding conditions you want, and at which times of day.
- Get the forwarding number once your plan allows it, choosing the same country as your existing number.
- Check your tariff for what forwarded calls cost, and whether your plan type allows forwarding to another number.
- Switch on forwarding with your carrier's codes, phone settings or admin panel.
- Test every condition you set, using the test plan below.
- Decide how you'll hear about handed-over calls, whether that's Slack, Zapier or checking the inbox at set times. Our article on AI receptionist handover to staff covers this.
- Write down how to switch it off, and keep it somewhere the team can find it.
How to test call forwarding before you rely on it
Don't assume it works because your phone said "diversion activated". Test it the way a customer would.
Test from a different phone
Always ring from a phone that isn't the one being forwarded, and ideally from a number the business doesn't know. Calling your own number from your own mobile can behave differently.
Test each condition separately
- All calls: ring the number. The AI should answer without your phone ringing.
- No answer: let your phone ring without picking up. Count the seconds until the AI answers. If voicemail answers instead, shorten the forwarding delay or lengthen the voicemail delay.
- Busy: ring the number while that line is already on another call.
- Unreachable: switch the forwarded mobile to flight mode, then ring it.
Test what the caller experiences
On each test call, check:
- The greeting names your business and sounds right.
- A common question gets a correct answer.
- A booking request offers real free times and, if you complete it, the booking appears in your bookings list.
- A request to speak to a person gets handled the way you want: details taken, a note saved, and the conversation flagged in your inbox.
- The call appears in your inbox afterwards.
Test at the times that matter
If you use different forwarding by time of day, test after closing time too. If you've set a time-based rule on a phone system, test just after the switch-over time.
Re-test whenever you change phone provider, tariff or handset. Forwarding settings sometimes reset quietly.
Troubleshooting common forwarding problems
| Problem | Likely cause | What to try |
|---|---|---|
| Voicemail answers instead of the AI | Voicemail delay is shorter than the no-answer forward delay | Shorten the forward delay or switch voicemail off |
| Code rejected | Wrong code for your network, or forwarding not allowed on your plan | Check your carrier's help page or ask customer services |
| Calls fail when forwarded abroad | Carrier blocks international forwarding | Use a forwarding number in your own country |
| Unexpected charges | Forwarded leg billed outside your allowance | Check your tariff; consider forwarding only out of hours |
| Callers say they were cut off | Forwarding destination unavailable or wrong number | Confirm the number, and that your plan is active |
Switching it off again
Forwarding is reversible in seconds. Use your network's cancel code (for example #21# on a BT landline, ##002# on Vodafone mobiles, *73 on Verizon), or turn it off in your phone or account settings. Your number goes back to ringing as before. Nothing about the AI receptionist changes your number itself.
Frequently asked questions
Do I need a new number to use an AI receptionist?
No. You keep your existing number and set it to forward calls to the AI receptionist's number. Customers keep ringing the number they know. With Klugon, the forwarding number costs $9 a month on top of a voice plan.
Will callers know their call has been forwarded?
Usually not. They dial your number and the AI answers with your greeting. There's no transfer message.
Which type of forwarding should I use?
If you want to keep answering when you can, use busy, no-answer and unreachable forwarding during the day, and forward all calls at night. If you never answer during the day, forward all calls.
Does call forwarding cost extra?
Setting it up is often free, but many carriers charge for the forwarded leg of each call, as if you'd made it. BT and Verizon both say charges apply to forwarded calls unless your plan covers them. Check your tariff.
Can I forward my UK number to a US forwarding number?
Avoid it. Forwarding abroad is often blocked or expensive. Choose a forwarding number in the same country as your existing number.
Can I forward a Pay as you go mobile?
Sometimes not. Vodafone, for example, says Pay as you go customers can only divert calls to voicemail. Check with your network.
Can I get the forwarding number during the free trial?
Not with Klugon. During the 7-day trial you test the assistant in your browser; phone numbers activate once the trial ends.
Can the AI receptionist forward the call back to me?
Not with Klugon. It can't transfer calls. When a caller needs a person, it saves their details with a note and flags the conversation for your team, so you can call them back.
Forwarding is the least glamorous part of setting up an AI receptionist and the part that most often goes wrong, usually because voicemail answers first or a code didn't take. Spend twenty minutes testing each condition from another phone, and you'll know it works before your customers find out it doesn't. For the bigger picture on covering your phone, see our guide on how to never miss a customer call, and for what's at stake, the guide to missed calls and lost revenue. If you're ready to try it, Klugon's AI receptionist has a 7-day trial.