Call forwarding unconditional means every call to your number goes straight to another number, and your own phone does not ring at all. Conditional call forwarding sends a call on only when something gets in the way: you are already on the phone, you do not answer within a set number of seconds, or your phone is off or out of coverage. A business uses the conditional kind to keep picking up its own calls and send only the missed ones to an answering service or an AI receptionist, on the same number it already prints on everything.
Key takeaways
- Unconditional forwarding sends every call away before your phone rings. Conditional forwarding has three triggers: busy, no answer and unreachable.
- On GSM networks the standard service codes are 21 for unconditional, 67 for busy, 61 for no answer and 62 for unreachable, defined in 3GPP TS 22.030. Carriers do not all use them.
- Verizon wireless uses *72 to forward all calls, *71 to forward only unanswered calls, and *73 to turn forwarding off.
- Voicemail and conditional forwarding compete for the same unanswered calls. Point the rule at an answering service and those calls stop reaching voicemail.
- Forwarding only moves the ring. Something still has to answer, take care of the caller and tell you what happened.
What call forwarding unconditional means
Unconditional forwarding, often shortened to CFU, is the always-on setting. The network sends every incoming call to the number you chose before your handset is even asked to ring. Your phone stays silent, and the caller has no idea the call went somewhere else.
The phrase usually shows up on screen in one of three moments. You dialed a forwarding code and the network replied with a status such as "Call forwarding unconditional: activated". You opened your phone's call settings and saw the option listed by that name. Or you noticed calls had stopped ringing, and the status check showed the line was forwarded. On an iPhone, the Call Forwarding setting is the unconditional kind, and a Call Forwarding icon appears in the status bar while it is on.
To check it on a GSM line, dial *#21# and the network replies with the current setting; ##21# erases it. Those are the standard interrogation and erasure forms in 3GPP TS 22.030, the spec that defines GSM phone codes. If you did not turn it on yourself, turn it off and call your carrier. Apple notes that iPhone blocks links that ask you to turn on call forwarding because scammers use them.
Conditional call forwarding: busy, no answer, unreachable
Conditional call forwarding lets your phone try first. The call only moves when one of three conditions is true, and on GSM networks each condition is a separate setting you can point at a different number.
| Type | When the call moves | GSM code | Your phone rings first |
|---|---|---|---|
| Unconditional | Always, on every call | 21 | No |
| Busy | You are already on a call or decline it | 67 | Yes, or you are on another call |
| No answer | Nobody picks up within the timer | 61 | Yes |
| Unreachable | Phone is off, has no signal or the battery died | 62 | No, it cannot |
| All conditional | Busy, no answer and unreachable together | 004 | Depends on the condition |
For a business, no answer and busy are the two that matter most. They catch the call you could not grab during a job and the second caller who rang while you were on the first. Unreachable covers the dead battery and the basement with no signal.
Call forwarding codes by carrier
Codes are where most guides go wrong, because carriers do not share them. These are the ones we could confirm on a carrier, platform or standards page. If yours is not here, use your phone's forwarding menu or ask your carrier.
| Line | Forward all calls | Forward unanswered calls | Busy and unreachable | Turn off |
|---|---|---|---|---|
| Verizon wireless | *72NUMBER | *71NUMBER | Not listed | *73 |
| AT&T wireless | Not listed | **61*NUMBER# | Busy **67*NUMBER#, unreachable **62*NUMBER# | ##61#, ##67#, ##62# |
| AT&T home phone | *72NUMBER# | *92NUMBER# | Busy *90NUMBER# | *73#, *93#, *91# |
| Rogers wireless (Canada) | *21*NUMBER# | *61*NUMBER# | Busy *67*NUMBER#, unreachable *62*NUMBER# | ##21#, ##61#, ##67#, ##62# |
| GSM standard (3GPP) | **21*NUMBER# | **61*NUMBER# | Busy **67*NUMBER#, unreachable **62*NUMBER# | ##21#; ##002# clears all, ##004# all conditional |
Sources: Verizon's call forwarding FAQ, Google Voice help for the AT&T wireless conditional codes, AT&T's home phone codes, Rogers' code list and 3GPP TS 22.030 for the standard. Google's page also notes that some resellers do not support conditional forwarding at all. T-Mobile is a GSM network, but we could not read its own support page to confirm its codes, so check with T-Mobile before relying on the standard ones.
How call forwarding and voicemail work together
Voicemail is where an unanswered call goes when nothing else is set. Conditional forwarding uses the same moment: the ring timed out, or the line was busy. So the two compete, and the call goes to one place or the other. Rogers says it plainly on its code page: conditional forwarding will not work while voicemail is activated.
- Forward to an answering service and voicemail goes quiet. Unanswered calls reach the service instead of your mailbox. That is the point: a person or an AI picks up, where most callers would not have left a message.
- Check what voicemail is set to catch. On some carriers you have to switch voicemail off before a conditional forward takes effect, as Rogers notes. If test calls still reach your greeting, that is the reason.
- Forward everything to voicemail when the line is closed for a week. Unconditional forwarding to your carrier's voicemail access number sends callers straight to the greeting; your carrier can tell you that number.
- Undo it and listen. Turning conditional forwarding off should send unanswered calls back to voicemail, but carriers handle the reset differently. Call yourself afterward and listen to where the call lands.
How many callers skip the message is the reason to forward at all. In a 2025 CallRail survey of 1,000 US consumers, a call tracking vendor's own study, 42 percent said they leave a voicemail and 82 percent said they would call a competitor when a business does not answer. If you do keep voicemail on some lines, the voicemail greeting scripts help.
Selective call forwarding
Selective call forwarding moves calls based on who is calling rather than on what your phone is doing. On a landline it is a list: AT&T's Select Call Forwarding forwards calls from 6 to 10 preselected numbers, depending on location, and leaves the rest ringing at home. You turn it on with *63 and off with *83, then follow the prompts.
Business phone systems do the same thing with more control: rules by caller, by time of day, or by which number was dialed. An AI receptionist adds a version of it on the answering side. It can transfer a caller who asks for a person or describes an emergency, and handle everyone else itself. The AI call routing guide covers that kind of rule.
Forward unanswered calls to an answering service, keep your number
The setup most small businesses want is simple: your phone rings as usual, and anything you miss goes to something that answers. You keep the number on your trucks, signs and listings, because the forward happens in the carrier network. The keep-your-number guide explains why no new number is needed. Here are the steps.
- 1
Get the answering number
Your answering service or AI receptionist gives you a number to forward to. On callflo.ai it is a local number on your account. - 2
Turn on no answer and busy
Use your carrier's codes from the table above, or the forwarding rules in your business phone portal. Point both at the answering number. Add unreachable if your phone often loses signal. - 3
Pick a ring time
Long enough to grab the calls you can take, short enough that callers do not hang up first. Start near 15 seconds. - 4
Test from another phone
Call your number and let it ring out. Then call while you are on another call. Both should reach the service, not voicemail. - 5
Write down the off code
Keep it in your phone notes. If you change services or go back to voicemail, you want it in one dial.
Forward on no answer is one layer of a wider plan. The call handling guide covers ring groups, time-of-day rules and what happens after hours.
Hear what picks up when your phone rings out
Call callflo.ai's own AI agent and ask it anything about your business. When you are ready, pick a plan: no setup fee, no contract, and you do not pay unless you are satisfied.
Starter is $39 a month on annual billing. Live on your line about 5 minutes after you sign up.
Which forwarding mode fits which business
| Situation | Forwarding mode | Why |
|---|---|---|
| Owner who works on site all day | No answer and busy | You still take the calls you can; the rest are answered |
| Office with a front desk until 5pm | Always, turned on at close | The desk answers the day, the service answers the night |
| A line nobody staffs, such as a leasing or ad number | Always | There is no point ringing a phone nobody holds |
| Field work with poor signal | No answer, busy and unreachable | A dead battery stops sending callers to silence |
| Calls from a few key clients only | Selective | VIP callers reach you anywhere, the rest stay put |
What a call answering and forwarding service adds
Forwarding is plumbing. A call answering and forwarding service is what sits at the end of the pipe: it answers the forwarded call, takes care of the caller, and sends the important ones back to you. There are two kinds. A human answering service puts a receptionist on the line, usually takes a message, and bills by the minute or the call. An AI receptionist answers every forwarded call at once and can finish the job on the call. The cost comparison prices both for the same month, and the answering service pages cover coverage by state and city.
callflo.ai is the AI kind. It answers every call 24/7, many at once, and trains on your website and the details you add, so it is live in about 5 minutes. It books appointments on your calendar, takes payments through Stripe with the card entered on the keypad, transfers calls by the rules you set, and texts callers a follow-up. You get a summary and transcript of every call in the dashboard and by text or email. You keep your number and forward it after hours, on overflow (busy or no answer) or always, or pick a new local number. Starter is 39 dollars a month on annual billing, or 49 monthly, with 120 minutes and no setup fee or contract, on the pricing page.