Disclosure: Futuro sells an AI receptionist that deploys directly to a phone line — the destination this guide forwards to — so we have a commercial interest in this page. The guide is deliberately vendor-neutral: every code and path is the carrier’s own; the destination can be any answering service. We never accept paid placement; see our Publishing Principles. Codes verified August 19, 2026.
What is conditional call forwarding?
Conditional call forwarding is a carrier feature that reroutes an incoming call to a second number only when a specific condition is met — you’re already on a call, you don’t pick up, or your phone is unreachable. Calls you answer behave exactly as they always have. The standard behind it, ETSI TS 122 082, defines these “call forwarding supplementary services” (ETSI, 3GPP TS 22.082).
The destination can be anything with a phone number: an answering service, a colleague — or an AI receptionist that answers, greets the caller by name, and books the appointment (glossary).
How is it different from unconditional forwarding?
Unconditional forwarding sends every call to the second number — your phone never rings; that’s the tool for full-time AI coverage. Conditional forwarding is the selective middle: you get first chance at every call, the AI catches only what slips past. Verizon draws exactly this line — *72 for all calls, *71 for no-answer/busy (Verizon).
Why do real estate agents and trades contractors use it?
Because their answer rate collapses exactly when the calls are most valuable. An agent mid-showing can’t answer the buyer calling off the yard sign; a plumber under a house can’t grab the emergency-job call; an HVAC tech on a roof can’t field the no-cool call in a heat wave. Most callers who reach voicemail hang up and dial the next name (missed-call economics). Conditional forwarding is the mechanical fix — a live answer on your existing number, only when you genuinely can’t take it — and paired with after-hours coverage, nothing goes to voicemail.
How many rings before the call forwards — and why does timing matter?
The no-answer condition isn’t instant: the carrier rings your phone first, then forwards. Standard cadence is two seconds of tone, four of silence — about six seconds per ring — so 3–4 rings ≈ 18–24 seconds (ITU-T E.180). Verizon describes its conditional delay as “three or four rings” (Verizon); T-Mobile lets you dial the delay in 5-second steps from 5 to 30 (T-Mobile); Ooma’s ring-then-forward defaults to 12 seconds (Ooma).
Why we recommend 3–4 rings, not 1–2 or 6+
At 1–2 rings you’ll rarely reach the phone in time; at 6+, many callers hang up first. 3–4 rings is the sweet spot: you keep first refusal, and the caller still hears an answer quickly.
The hidden benefit: those rings are when the AI loads the caller’s file
Here’s the part nobody talks about. A forwarded call carries the original caller’s number with it — ETSI TS 123 082 documents the signaling (ETSI), and carriers expose it as a caller-ID choice: Ooma can show the original caller’s number (Ooma); RingCentral lets you choose the original caller over your own (RingCentral). The FCC confirms this is the legitimate design — forwarding preserves real caller ID, unlike spoofing, which is what’s illegal (FCC; FCC STIR/SHAKEN).
So during rings 1–3, while your phone rings, our memory system looks the caller up — name, history, open job, preferences — and pre-loads their file. When the AI answers, it already knows who’s calling. The ring delay isn’t dead air; it’s the look-up window — the mechanism behind our AI memory system.
How do you set it up on any carrier?
Every carrier wraps the same mechanism in different packaging — learn the pattern once and each carrier section becomes a lookup: get the destination number, activate busy and no-answer, set the ring delay, test — about ten minutes.
The universal four moves
One: get your AI receptionist’s number. Every answering service — ours included — gives you a dedicated number to forward to; on Futuro’s trial it arrives with your account, and a guided setup call walks this sequence with you. Two: activate the conditional codes — star code or portal toggle for busy and no answer, never the unconditional code. Three: set the ring delay to three or four rings where the carrier exposes it. Four: test with a second phone. Enter the number as ten digits, no spaces — notation per ITU-T E.123, numbering plan per ITU-T E.164 — because some carriers reject a stray leading 1 or punctuation.
The hub table: every path at a glance
The quick-reference card — print it, save it, stick it in the truck. We publish it as a citable dataset under CC-BY; per-carrier deep-dives roll out over the coming weeks.
| Carrier / platform | Activate conditional forwarding | Turn it off | Ring delay |
|---|---|---|---|
| Verizon | Dial *71 + 10-digit number | Dial *73 | Carrier-set, ~3–4 rings |
| AT&T Wireless | Device settings; GSM codes per standard | Settings toggle; ##004# clears conditions | Via support or GSM timer code |
| AT&T Phone (landline) | *90 busy / *92 no-answer + number + # | *91# / *93# | Configurable in online account |
| T-Mobile | **61*1+number# (no reply), **67*1+number# (busy) | ##61# / ##67#; ##004# resets all | **61*1+number**seconds# — 5 to 30 |
| Google Voice | Settings → linked numbers (simultaneous ring) | Toggle the linked number off | Not exposed — see below |
| RingCentral | Call Handling & Forwarding rules | Delete or disable the rule | Per-rule ring settings |
| Ooma | *72 or portal Call Handling routing | *73; *74 toggles | “Ring for” menu, default 12s — raise it |
| Grasshopper | Extension call routing + schedules | Re-route the extension | Per-extension ring settings |
Two warnings. First, billing: forwarded calls consume airtime — Verizon and AT&T both document per-minute treatment on forwarded legs — so a flat-rate answering plan pairs better than a per-minute one. Second, none of the majors forward to international numbers.
How do you set it up, carrier by carrier?
Eight paths, each with the exact code or menu, the ring-delay step, and the undo. Codes were verified against the linked official documentation on August 19, 2026 — the linked page is always the authority.
Verizon: *71 is the whole trick
Dial *71 plus your ten-digit AI number, wait for the confirmation tone, and you’re live — Verizon calls this No Answer/Busy Transfer in its forwarding guide and activation walkthrough. Your phone rings three or four times first; only what you miss forwards. The setting also lives in My Verizon; *73 turns it off per the deactivation guide.
AT&T: two different worlds
AT&T Wireless first. On iPhone, the supported path is Settings → Apps → Phone → Call Forwarding per AT&T’s device tutorial and Apple’s guide — but that switch is unconditional: every call forwards, your phone stops ringing, and forwarding overrides your wireless voicemail. For conditional behavior, use the GSM codes AT&T’s network implements — **61* plus the number for no-reply, **67* for busy, per ETSI TS 122 030 — or call 611 with the support script below. On AT&T Phone landline and business service the codes are explicit: *90 for busy, *92 for no-answer, each followed by the number and #, per the star-code reference; *91# and *93# switch them off.
T-Mobile: the most configurable of the majors
T-Mobile publishes the full GSM set on its short-codes page: **61*1+number# forwards no-reply calls, **67*1+number# covers busy, **62*1+number# catches unreachable — the off-grid condition nobody else exposes this cleanly. Deactivate with ##61#, ##67#, ##62#, or reset all conditional forwarding with ##004#. Uniquely, the ring timer lives in the dialer: **61*1+number**seconds# sets a 5-to-30-second delay — dial 20 and you’ve landed the three-to-four-ring window. If calls misbehave, the troubleshooting page walks the same ##004# reset a rep would run.
Google Voice: powerful, but not truly conditional
Google Voice has no star codes; forwarding runs through linked numbers. The documented sequence — laid out in this university IT guide — is Settings → New linked number → enter the AI number → verify with Google’s code by text or call → toggle it on. The honest caveats: linked numbers ring simultaneously, not conditionally — your cell and the AI number ring together, whoever answers first wins — workable solo, not an overflow. Turn call screening off or Google intercepts the call before forwarding. And the verification code goes to the destination number — on our guided setup call we catch it live. Google Voice suits a one-person shop; everyone else should forward at the carrier level.
RingCentral: rules, not codes
As a full VoIP system, RingCentral does this with rules, documented on its call forwarding overview: per-extension Call Handling & Forwarding settings with work-hours and after-hours behavior, sequential or simultaneous ring groups, and custom rules. The AI number goes in the ring sequence — typically last, after your desk phone and app — so it catches only what humans miss. Two details from RingCentral’s call handling documentation: you can choose whether forwarded calls display the caller’s ID or your own number — choose the caller, always — and custom rules override schedules — which matters when testing.
Ooma: the small-business favorite, key-press gotcha included
Ooma Office covers both worlds. From a desk phone, *72 plus the number sets immediate forwarding, *73 clears it, *74 toggles — per its on/off guide. For the conditional setup, use the portal’s Call Handling page: ring your devices first, then “send to” the forwarding number, ring duration raised from the default twelve seconds toward twenty, per the routing guide; a dedicated offline forwarding switch covers unreachable. Two settings matter for AI answering: show the original caller’s number, and turn off “require key press on answer” — an AI answers deterministically, so the prompt only adds a dead second.
Grasshopper: extension routing with schedules
Grasshopper is a virtual system — no desk phones, everything routes to cells and external numbers — a natural fit here. Per its official setup guide, you point the number at an extension via Call routing → Direct connect to extension; the extension’s forwarding settings and schedules decide where calls land and when. Put your own cell early in the list and the AI number last, and callers hit a human first and an AI never. One caveat: business-hours schedules make after-hours routing clean, but intra-day overflow depends on your extension configuration — test it before a busy Monday does.
Landlines and every other VoIP: the *72 family, plus portals
Traditional landlines and most hosted VoIP providers speak some dialect of the same star-code family — *72 all calls, with *90 busy and *92 no-answer as the common conditional pair, exactly as AT&T’s landline reference documents them — and nearly every hosted provider exposes forwarding rules in a web portal. Two cautions. Landline codes vary more than anywhere else, so treat the pattern as a hypothesis and confirm with the support script below. And if your number lives on a VoIP platform, your forwarding rules live behind a login — secure it like your cash drawer; call processors and voicemail are part of the attack surface NIST’s VoIP security guidance has flagged for two decades.
What should you tell your carrier’s support rep?
The most fragile step in this setup is a phone call: a frontline rep hears “I want to forward my calls” and turns on the wrong thing. The fix is vocabulary.
The script, line by line
Open with the exact feature name: “I want to set up conditional call forwarding — the busy and no-answer conditions only — to an external U.S. number.” On Verizon, add the product name, “No Answer/Busy Transfer,” from its documentation. If the rep stalls, standards vocabulary unsticks things: the conditions are formally CFB (call forwarding busy) and CFNRy (call forwarding on no reply), per the ETSI specification every mobile network implements.
The sentence to avoid
Never open with “I want all my calls to go to another number.” That maps to unconditional forwarding — *72 and its cousins — and a rep following it will silence your phone entirely. If that already happened, the undo section fixes it in a minute. Before hanging up, confirm the ring delay — “and my no-answer timer is set to about twenty seconds?” — the detail reps most often leave at default.
Why do calls still hit voicemail?
Nine times out of ten, a failed setup is one of five causes — all fixable once you can name them.
The ring-delay race
Your carrier’s voicemail is itself a forwarding destination with its own timer. If voicemail grabs calls at 25 seconds and your no-answer forward fires at 30, voicemail wins every race. Shorten the forward timer — T-Mobile’s delay code is a one-dial fix — or ask the carrier to move voicemail back. The reverse failure also exists: unconditional forwarding overrides voicemail entirely per AT&T, so if messages stopped landing, check for a stray *72.
Loops, strays, and interceptions
Forwarding loops happen when two numbers point at each other — your cell forwards to the AI, an old rule forwards back — producing instant busy signals or silent drops; audit every rule on both numbers (the standards track forwarding chains, so carriers can see the loop even when you can’t). Stray unconditional forwarding is the *72 mistake above — the symptom is a phone that never rings. Interception is platform-specific: Google Voice’s call screening answers before forwarding; Ooma’s key-press option can hand the call to your cell’s voicemail instead. When in doubt, nuke and rebuild: T-Mobile’s troubleshooting flow starts with ##004#, a full conditional reset.
One worry you can set aside
Owners sometimes hesitate because forwarding sounds like it could tangle their number in spam filters. It doesn’t: forwarding preserves the caller’s real ID, and the FCC’s spoofing rules target falsified ID, not forwarded calls. STIR/SHAKEN — mandated under the TRACED Act, described on the FCC’s call authentication page — verifies the originating number, exactly what a forwarded call carries. Your number’s reputation is untouched. For calls you never wanted anyway, the FCC’s robocall guidance is the right toolset.
How do you test it in five minutes?
Never let Monday morning be the first time the forwarding fires. One borrowed phone and five minutes proves the chain before a customer depends on it.
The three-call protocol
Call one, no-answer: from a second phone, call your number and let it ring. Count — three to four rings before the forward fires — and confirm the AI answers, not your old voicemail. Call two, busy: put your line on a call, then dial in again; the AI should answer immediately — the busy condition has no timer. Call three, the context check: hang up, dial once more, and listen to what the AI knows. On a Futuro line the agent greets the returning caller with their file already open — the memory system spending the ring delay on lookup — but whatever service you use, confirm it saw the second phone’s real number, not yours. T-Mobile’s troubleshooting guide uses the same self-call pattern. Log what you saw: rings before forward, who answered, which caller ID showed.
What a pass looks like
You answer the calls you can reach on ring one or two, exactly as before. The calls you miss land on an AI that already knows who’s calling. Voicemail becomes the backup’s backup. If any leg fails, troubleshooting maps symptom to fix; undo codes are below if you want it gone.
How do you turn it off?
Every setup here reverses in under a minute; nothing about your number, plan, or voicemail changes permanently. Keep the undo codes next to the setup codes — same card, other column.
The universal undo
Verizon: dial *73 — clears conditional and unconditional forwarding, per the deactivation guide. T-Mobile: ##61#, ##67#, ##62# clear individual conditions; ##004# resets all, per the short-codes page. AT&T: *91# and *93# clear busy and no-answer on landline, *73# clears all-call, per the business reference; on wireless, toggle the Settings switch back or clear the GSM conditions. Ooma: *73 from the extension phone, or set Call Handling back to voicemail in the portal. Google Voice: toggle the linked number off. RingCentral and Grasshopper: disable the rule or re-route the extension. Then rerun one test call and confirm your own voicemail or your own voice answers.
How we researched this page
Setup guides live or die on whether the codes still work, so this page is documentation-first and dated like milk.
Evidence level: official documentation, verified line by line
Every code, menu path, timer, and caveat here was verified against the linked official source on August 19, 2026 — carrier support pages, platform documentation, the ETSI/3GPP forwarding standards those carriers implement, the ITU specifications underneath, and the FCC’s caller-ID rules. Where two sources disagreed — and community threads disagree with carrier documentation constantly — the official page won. Where a carrier’s page was silent, we say so inline rather than borrow from a forum.
What we did not do
We did not place live test calls on every carrier, MVNO, and prepaid variant — Verizon’s own guide notes some retired plans differ, and MVNOs inherit their host network’s codes with occasional gaps. We did not cover international carriers; this guide is U.S.-scoped. Per-carrier deep-dives with screenshots roll out as companion pages over the coming weeks.
The carrier-change watch
Codes change when carriers retire features or merge menus, and a stale setup guide is worse than none. This page carries its date openly — last verified August 19, 2026 — and we re-check every code on each revision. If your carrier contradicts this page, the linked page is the authority: editorial@futurocorp.com, per our corrections policy.