How to set up AI phone answering with conditional call forwarding

Conditional or unconditional: pick the right one

Call forwarding is how an AI answering line gets your calls. There are two types, and they do different jobs.

Conditional forwarding is usually the better fit for daytime. Your team takes the calls it can take, and the AI answers the calls that would otherwise go to voicemail. Unconditional forwarding is a switch you turn on and off yourself, so use it only when you know the line will not be answered.

Forwarding is set up on the phone line, so the rules are the carrier’s. This article covers the carrier codes for busy and no-answer forwarding. If your business runs on a phone system, the setup is in that system, as explained further down. For the overflow side of the service, see overflow and busy-line answering. Our AI receptionist page explains how the answering line fits with the rest of your phone set-up.

The star codes, and why they differ

Many guides start with the common GSM codes. They come from the 3GPP mobile standard (TS 22.030, published by ETSI), which gives each forwarding type a service code: 67 for busy, 61 for no reply and 62 for not reachable. Registering a forwarding number takes the form **code*number# (the standard also allows a single star), and erasing it takes ##code#:

• Busy: **67*[forwarding number]#. Cancel with ##67#.
• No answer: **61*[forwarding number]#. Cancel with ##61#.
• Unreachable: **62*[forwarding number]#. Cancel with ##62#.

Treat these as common GSM codes that vary by carrier, not as a rule. A standard describes what a phone should understand. Whether a code works on your line is up to your carrier and plan, and many US lines use their own codes instead. Verizon’s own page, for example, uses *71 for conditional forwarding. The code your carrier documents for your line is the one to use.

Here are the two carrier pages we checked:

Verizon (mobile, per its support article)
  Busy or no answer:  dial *71, then the forwarding number
  Cancel:             dial *73
  All calls:          dial *72, then the forwarding number

AT&T Phone (home phone, per its support article)
  Busy:               *90, then the forwarding number, then #
  Cancel busy:        *91#
  No answer:          *92, then the forwarding number, then #
  Cancel no answer:   *93#
  All calls:          *72, then the forwarding number, then #
  Cancel all calls:   *73#
  Unreachable:        no code listed on that page

AT&T’s page also says that not all features can be managed with a star code, so check the account settings if a code does not take effect. The AT&T page is for the home phone service. A mobile line on the same account may use other codes.

Set up the forwarding, step by step

1. Get the AI line number. Confirm it is the number the assistant answers on, and that it is a US number. Verizon does not forward to non-US numbers.
2. Check the plan. Forwarding may be free on a current plan, but forwarded calls use your airtime, so check the minutes you have.
3. Dial the code from the line you are forwarding. Wait for the confirmation tone or voice message. Do not assume it worked because the phone went quiet.
4. Set the no-answer delay if your phone allows it. The delay you can choose depends on your carrier and phone, so test how many rings your team actually gets before the call forwards.
5. Write the codes down. Keep the activation and cancel codes in your front office binder, with the carrier’s support number.
6. Use the account page if codes fail. Verizon says you can also set forwarding in My Verizon. Its article also warns that an extra key press can stop the number from being recognized, so enter the number again if the test fails.

If your business runs on a phone system or VoIP

Business phone systems and VoIP lines usually set forwarding on an admin page or in the phone system’s settings, not with star codes. Use that page for the rules on busy, no answer and unreachable. Ask your provider which of the three the system supports, and whether the forwarding destination can be an outside number. The codes in this article are for carrier lines.

Test every case before you rely on it

Run this checklist once after setup and again after any carrier or phone change. Log the date, time and result for each line.

• Busy. Call the line from a second phone while the first line is on a call. The AI answers.
• No answer. Let the line ring past your delay. The AI answers.
• Unreachable. Turn the phone off or switch it to airplane mode, then call from outside. The AI should answer. If it does not, check whether your carrier offers an unreachable code at all, and rely on the busy and no-answer tests.
• Two kinds of caller. Test from a mobile phone and a landline. Both should reach the AI.
• What the caller hears. The assistant says it is an AI assistant and offers a person or a message.
• What your team gets. The lead summary reaches the person you named, by text or email, in the way you agreed.
• Cancel. Dial the cancel code for each type, call again, and confirm your phone rings. If it does not, repeat the cancel step on the account page.
• Re-enable. Set the forwarding again and repeat the busy test. Keep the codes you used.

If a test fails, change one thing and test again. Common causes are the wrong number, a code typed with a missing star or hash, or a delay that is longer than the test call waits.

Common mistakes

• Dialing the code with a missing star or hash. A code with a missing character often does not take, so dial the whole string again rather than patching the end of it.
• Setting the code on the wrong line. A business with two numbers has two sets of forwarding settings. Confirm which number each code changed.
• Leaving a test forward on. If you forget the cancel code after a test, the AI keeps answering calls your team would have taken. Check the forward status after every test.
• Testing from one phone only. A busy test from your mobile proves little about a landline caller. Use both.
• Changing the carrier or the phone without retesting. A new SIM, a new handset or a plan change may change the settings. Run the checklist again.

Who this is for, and who can skip it

A small office with one or two lines, a team that answers in the day and no one who answers at night, will get most of the value from conditional forwarding. A business with a receptionist who picks up every call during business hours may only need unconditional forwarding for the hours after close. A business that uses a phone system with hunt groups and voicemail rules should set those rules in the phone system first, then forward only the calls that reach the end of the group.

We set up the AI answering line as part of the AI assistant service, and each step is optional. PhoneAnswer is our self-serve AI receptionist if you want to set it up yourself, and CallReply is our done-for-you AI phone agent if you want it built and run for you. For the prices, see AI assistant pricing. A free demo shows how your business looks to customers today, including the calls that go unanswered.

Published October 26, 2026. Updated October 26, 2026.