How to Forward Calls to an Answering Service (Carrier Codes)

Forwarding is the whole migration. You do not port a number, change your cards, or touch your website - you dial a short code and every call your business would have lost lands somewhere that answers. It takes about eight minutes and it is reversible in one more code, which is why we tell people to test an answering service this way before anything else. The catch is that four different forwarding rules exist, the codes differ by carrier, and one silent failure - carrier voicemail beating your forward to the call - accounts for most of the "it didn't work" support tickets we see. This guide covers all of it.

The short answer

Your answering service gives you a destination number. You tell your carrier to send calls there under a condition you choose. On a Verizon mobile line that is *72 plus the number for every call, or *71 plus the number for unanswered calls only, with *73to switch it off. On AT&T and T-Mobile it is the GSM-style codes - **21*number# for all calls, **61*number# for unanswered, **67*number# for busy - with ##004# to clear everything. On VoIP you skip the codes and set a forwarding rule in the admin panel. You keep your number either way; nothing is ported and nothing is permanent. The background on that is in can I use my existing number with an AI receptionist; this guide is the actual keypad work.

The four forwarding rules

Every phone system in the world implements the same four conditions, even when it hides them behind friendlier names. Knowing which is which is most of the job:

The three conditional rules are usually set separately and are usually wanted together - a call that rings out, a call that arrives while you're on another one, and a call that arrives while your phone is dead in a basement are all the same event from the caller's side: nobody answered. Setting only the no-answer rule and forgetting the busy rule is the most common half-finished setup, and it fails on exactly the calls that matter most - the second and third callers during your busiest hour. That is also what makes parallel answering worth having on the receiving end.

Which rule you actually want

Our honest recommendation for the first two weeks is the conditional set. It has no downside worth naming: the calls you answer stay exactly as they were, and you get a log of everything you were previously losing. Read the transcripts, then decide whether answering everything first is the better experience - for most businesses with a real front desk it eventually is, for the reasons in replacing a front desk receptionist with AI.

Forwarding a mobile line

Dial the code from the phone whose calls you want forwarded, exactly as if it were a phone number, and wait for the confirmation tone or message. Codes as the three big US carriers document them:

Two notes that save an afternoon. First, enter the destination in full with the country and area code - **61*15551234567#, not a seven-digit number - because the switch is not guessing your area code. Second, ##004# is the universal reset on GSM networks: it clears all conditional forwarding at once, which is what you want when you have been experimenting and no longer trust what is set. On Verizon, the official FAQ also lets you set forwarding from the My Verizon app instead of the keypad, and T-Mobile documents its codes on the self-service short codes page. If a code returns "invalid MMI", that is the network refusing it, not your phone - use the carrier app or account portal.

The voicemail race (the #1 failure)

This is the one thing to understand before you touch the keypad, and it is why most people's first attempt appears to do nothing at all.

There are exactly two clean fixes, and you should do one of them:

1. Shorten the forwarding timer. T-Mobile documents a code for this - the same **61* form with a seconds value appended, settable between 5 and 30 seconds. Set it to 15 and the forward wins comfortably.
2. Turn carrier voicemail off on that line. Blunter and more reliable: with nothing to lose the race to, the forward is the only outcome. This is the right choice once you trust the service, because two message inboxes - a voicemail box nobody checks and a call log somebody does - is worse than one.

Doing both is fine. Doing neither and wondering why nothing happens is the default outcome, and it is the reason we walk new accounts through a live test call rather than trusting the setup screen.

Landlines, VoIP and PBX systems

Traditional landline

Copper and cable landlines generally use *72 to enable and *73 to disable, with *71 or *68 for the busy/no-answer variant depending on the provider. Dial from the line itself, listen for the stutter tone, and note that some providers require you to hear the destination ring before the setting sticks.

VoIP and hosted PBX

If you are on RingCentral, Dialpad, 8x8, Nextiva, Zoom Phone, Google Voice or any hosted PBX, do not use star codes. Set the destination in the admin panel instead. You get three things the carrier cannot give you:

• Schedules. Business hours to your team, everything else to the service, automatically, forever - no more remembering to dial anything on a Friday evening.
• Ring-then-overflow. Ring the desk for twelve seconds, then hand off. This is the setup most offices actually want and it is impossible to express with a star code.
• Per-number routing. Point three DIDs at the same service and let it greet each one differently - the sales line, the service line, the Spanish line.

One warning specific to PBXs: check whether yours rewrites outbound caller ID. A PBX that stamps your main number on the forwarded leg makes every single call look like it came from your own office, which destroys callback numbers, CRM matching, and returning-caller recognition. It is a one-line setting and a five-minute test.

Testing it in eight minutes

1. Set the rule from the line you want forwarded, using the destination number the service gave you. Wait for the confirmation tone.
2. Call from a phone that is not on your account - borrow one. Calling yourself from the same line or the same account can behave differently and will teach you the wrong lesson.
3. Let it ring out if you set the no-answer rule. Count the rings and note whether the service or voicemail answers. If it is voicemail, go back to the section above; nothing else is wrong.
4. Test the busy path. Get on a call, then have someone else dial in. This is the leg everybody skips and the one that fails most often in practice.
5. Check the log.Open the service's call log and confirm three things: the caller's real number appears, the correct greeting played, and the transcript is complete.
6. Test the escape hatch. Ask to speak to a human and confirm the transfer rings the right phone. A forward that cannot get back to you is a trap, not a safety net.

Six things that quietly break forwarding

• The forwarding loop. Forwarding to a number that forwards back gives callers a fast busy tone or dead air, and it is easy to build accidentally when a service hands you a number that already points at your mobile.
• Setting the code on the wrong line. Codes apply to the line you dial them from. Forwarding your personal mobile because it was the phone in your hand is a memorable afternoon.
• Forgetting the busy rule. No-answer forwarding does nothing for the second simultaneous caller. Set all three conditional rules or accept that you are still losing your busiest hour - the arithmetic of which is in the cost of a missed call.
• Plan minutes. On many carriers the forwarded leg is billed to your line like an outbound call. Irrelevant on unlimited talk; relevant on pooled business minutes and high volume.
• Number formats. A destination entered without a country or area code fails silently on some switches and succeeds into the wrong area code on others.
• Leaving it on after you stop. If you cancel a service, clear the forward the same day (*73 or ##004#). An orphaned forward points your business line at a number that no longer answers - the single worst state your phone can be in.

Turning it off again

*73 on Verizon and most landlines. ##004# on GSM networks to clear every conditional rule at once, or the specific off-codes (##21#, ##61#, ##67#, ##62#) if you want to remove one and keep the others. On VoIP, delete the rule in the panel. Listen for the confirmation, then place one real test call to be certain - the code silently failing is rarer than the human assuming it worked.

This reversibility is the argument for evaluating an answering service by forwarding rather than by demo. You are risking one code in each direction and no contract - see whether an AI receptionist requires a contract - so the only real evaluation, your own callers on your own number, costs you two weeks and nothing else.

Forwarding vs porting your number

Almost nobody should port on day one. Forward, run two weeks, read the transcripts, and port later only if the old line has stopped earning its bill.

What to set up on the receiving end

A forward is only as good as what answers. Before you point real calls anywhere, make sure the destination knows your hours, your services, your prices and your escalation rules - the practical checklist for that is in AI receptionist prompts, and if the reason you are forwarding is nights and weekends, the coverage patterns are in the after-hours answering service guide and the 24 hour guide. If you want the number to point at, our pricing page has plans that start month-to-month, and the missed-call calculator will tell you what the calls you are currently forwarding to voicemail are worth.