How to handle overflow calls when you're already with a client
The second call that arrives while you're on the first is the one you never hear about. Here's how to catch it without turning your business into a phone tree.
Updated 2026-07-28 · Written by RingOwl, an AI answering service — our bias is disclosed in every section that mentions us
The short answer
Overflow calls are the ones arriving while you're already on a call or with a client, and for most small businesses they vanish silently — the caller hits voicemail or a busy signal and you never learn they rang. The fix has three levels. Free: carrier busy-forwarding (**67#) sends only those calls to a second phone, a colleague, or voicemail, and a missed-call auto-text catches the rest. Middle: a shared line or a simple hunt group so a second person's phone rings. Full: an overflow answering service, human or AI, that picks up the second call properly and can book. The thing to avoid at every level is solving it with an IVR menu — 'press 1 for sales' is what makes a small business feel like a call centre, and it's usually unnecessary at small-business call volumes.
- 1Busy-forwarding (**67#) routes only the calls that arrive while you're on another line — free, five minutes
- 2Overflow calls are invisible by default; you can't manage what you never see
- 3An answering service handles overflow in parallel, so the fifth simultaneous call is answered like the first
- 4Avoid IVR menus at small-business volumes — they cost more goodwill than they save time
- 5Whatever you choose, make sure overflow calls show up in the same place as everything else
Why overflow is worse than it looks
A regular missed call leaves evidence — a missed-call notification, maybe a voicemail. An overflow call often doesn't. Depending on your carrier and setup, a caller arriving while you're mid-conversation may get a busy signal, may be dropped straight to voicemail without ringing, or may hear ringing that you never perceive because you're on the line.
So the first problem isn't handling overflow calls. It's that most small businesses don't know how many they get. Before choosing a fix, check your carrier's call log or usage report for calls that arrived during other calls — the number is usually higher than people expect, and it clusters at exactly your busiest times.
That clustering is what makes overflow expensive out of proportion to its volume. The calls you lose are concentrated in the periods when demand is highest.
Level 1 — Free, and takes five minutes
Carrier busy-forwarding handles this specific case natively. Dialing **67#<number># forwards calls that arrive while you're on another call, and nothing else — your normal calls are untouched. Cancel with ##67#.
Where you point it depends on what you have. A business partner or assistant's mobile is ideal. A second phone you can check between appointments works. Even pointing it at voicemail is an improvement over a busy signal, because at least the caller can leave a message and you get a notification.
Pair it with missed-call text-back so any call that still goes unanswered triggers an immediate text. Together these two changes cost nothing and take under half an hour, and they convert the silent-failure case into something visible.
Level 2 — A second line that rings
If there's more than one of you, a hunt group — calls ring one phone, then the next, then the next — is the traditional answer and most business phone systems support it. Google Voice, RingCentral, Grasshopper, and most VoIP providers offer some version.
The trade-off is coordination overhead. Hunt groups work well when everyone genuinely can answer and badly when the second phone belongs to someone in a meeting. They also don't solve after-hours, since the whole group is off at the same time.
This is the level where a lot of small businesses reach for an IVR — 'press 1 for bookings, press 2 for accounts' — and it's usually a mistake. Menus pay off at high volume with genuinely distinct departments. At small-business volumes they add friction for every caller to solve a routing problem you could handle by just answering. If you're considering one, count how many calls a day would actually be routed differently. It's often not many.
Level 3 — An overflow answering service
Both human and AI answering services will take overflow, but they behave quite differently when several calls land at once, and that's the entire scenario here.
A human service has finite operators shared across client businesses. Your overflow call joins a queue. Usually that's fine; during a genuine spike, hold times appear precisely when you least want them.
An AI service answers in parallel with no queue — the fifth simultaneous call is answered as quickly as the first, because there's no shared resource to contend for. For overflow specifically, that property matters more than it does for general answering, since overflow is by definition a concurrency problem.
The setup that keeps this from feeling impersonal: use busy-forwarding rather than unconditional forwarding. Your callers reach you whenever you're free. Only the ones who'd otherwise have hit a busy signal reach the service, and they get a real conversation instead of a dead end.
Keeping it from feeling like a call centre
The perception problem is rarely about whether a human answered. It's about whether the caller got somewhere useful. A well-configured AI that knows your business and books the appointment is a better experience than a human who takes a message and gets your prices wrong.
- Forward on busy only. Never route calls to a service you could have answered yourself.
- Skip the menu. At small-business volume, answering and asking is faster for the caller than any tree.
- Make sure whoever or whatever answers uses your business name and knows your hours, services, and prices. Generic answering is what actually reads as impersonal, not the fact of delegation.
- Let the caller reach a person when they ask. An overflow handler that can't escalate is a wall.
- Keep everything in one place. Overflow calls should land in the same summary inbox as the rest, not a separate portal you'll check twice.
How RingOwl fits overflow
Our product is an AI receptionist, so it answers overflow calls in parallel with no queueing, using your business name, hours, and services. Combined with carrier busy-forwarding, calls only reach it when your line is already engaged — you keep every call you were able to take.
It books into Google Calendar and Appointo during the call, and sends a summary of every overflow call to the same place as everything else. Pricing is $49, $99, or $199 a month flat, so a spike in overflow doesn't produce a spike in your bill. Trial is 7 days with 30 minutes and no credit card.
Questions
Common questions
How do I find out how many overflow calls I'm getting?+
Check your carrier's call detail records rather than your phone's log — the phone often doesn't register a call that arrived while you were on another. Most carriers expose this in the online account under usage or call history. Look for inbound calls whose timestamps fall inside another call's duration.
Is a phone menu (IVR) worth setting up?+
Usually not below a few dozen calls a day with genuinely distinct destinations. Menus impose a cost on every caller to save routing effort on a minority. Count how many of your calls would actually route differently before building one.
Can I forward only when I'm on another call?+
Yes — that's exactly what **67# does. It's independent of the other forwarding rules, so you can enable busy-forwarding without touching what happens when you simply don't answer.
Will an answering service know enough to handle my overflow calls?+
It depends entirely on setup. Any service worth using takes your hours, services, prices, and common questions up front. The failure mode is a service configured with a bare script that then improvises — ask what happens when a caller asks something outside the configuration, and make sure the answer is 'offers a callback' rather than 'makes something up'.
What about calls that overflow after hours?+
Different problem, same tools. Busy-forwarding only covers calls arriving during another call; after-hours calls need no-answer forwarding or a service covering that window. Our after-hours guide covers the options.
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