Call forwarding answering service, rule by rule
An answering service only hears the calls your phone line sends it. With Asyntai, your line forwards calls to a number in your own Twilio account, and the AI agent answers there. The forwarding rules you switch on decide which calls arrive: the unanswered ones, the busy ones, the ones when your phone is off, or all of them.
Each rule sends a different set of calls to the AI
Call forwarding is a setting on your phone line, not in Asyntai. A line can offer several rules, and you can switch on one or combine a few. Here is what each one hands to the answering service.
No answer
Your phone rings first. If nobody picks up within the delay you set, the call moves on to the Twilio number. The AI gets the calls your team let ring, and the team keeps every call it can take.
“I rang twice this morning, is anybody there?”
Busy
The call moves on when your line is already in use. The AI gets the next caller while the first one is still talking to your team. Ask your provider how call waiting affects this rule.
“Your line has been busy all morning.”
Unreachable
The call moves on when the network cannot reach your phone: no signal, the battery is dead, or the phone is switched off or in airplane mode. The AI gets the calls that would otherwise go nowhere.
“It didn't even ring, it went straight through.”
Always
Every call moves on at once, and your own phone stays silent. The AI gets the whole line, which suits closing time, a holiday, or a line you want the agent to answer first.
“Are you open over the long weekend?”
On a schedule
Some business phone systems can switch forwarding by time of day. Where yours cannot, switch the always rule on when you close and off when you open. The AI gets the evenings and weekends.
“I know it's late, I just want to check pick-up times.”
No forwarding at all
Publish the Twilio number itself as your business line. The AI answers every call first and, in your Escalate to Human hours, transfers a caller who asks for a person to your team.
“Can I talk to someone about my dog's stay?”
Every forwarded call meets the same well-briefed agent
The rule decides which calls arrive. What the caller hears then comes from your own material, and it is the same at 2 pm on a busy line as at 2 am with the phone switched off.
- Your website, read page by pageServices, prices you publish, opening and pick-up times, directions. When a page changes, have Asyntai read it again.
- Documents you uploadRequirements, policies and price sheets, as PDF files or pasted text. The next call uses a changed document.
- Your AI InstructionsPlain-English rules, for example which requests always become a callback request, and when to offer a transfer.
Stop a missed transfer from looping back to the agent
A transfer rings the transfer number for up to 20 seconds. If nobody answers, the caller comes back to the agent, which apologizes and takes a callback request. That only works when the transfer phone does not forward the call on first.
- No-answer delay above 20 secondsIf the transfer number is the same phone that forwards to the Twilio number, set its no-answer delay to more than 20 seconds, so the transfer times out before the forwarding starts.
- Busy, unreachable and always rules fire at onceOn the transfer phone, these rules can send the transfer straight on to the Twilio number. If that phone uses any of them, transfer to another phone.
- A second phone is the simple fixA manager's mobile or a back-office line without forwarding to the Twilio number keeps transfers and forwarding apart.
Give your forwarding rules a number to send calls to
The destination of every rule is one number in your own Twilio account. Twilio bills you for that number and its call minutes. You need an Asyntai Standard plan or higher and a paid Twilio account, because a trial account cannot be used.
- Create an Asyntai account and add your website. The pages are read in a few minutes. Upload your requirements and price documents.
- Write the greeting on the Voice Agent page and try a free test call in the browser before any call is forwarded.
- On the Phone Calls page, connect Twilio with the Account SID and Auth Token, and press Import next to the number that will receive the forwarded calls.
- Set a transfer number and your hours under Escalation, then switch on the forwarding rules on your own line, pointed at that Twilio number.
Forwarding rules and what they send to the AI
Use this table to pick your rules. The codes are the standard GSM codes for mobiles; replace "number" with your Twilio number in international format.
| Rule | When the call moves on | What the AI answers | Standard GSM code |
|---|---|---|---|
| No answer | After your phone rings for the delay you set | Calls nobody picked up | **61*number# (with a delay: **61*number**25#) |
| Busy | When your line is already in use | Callers who would hear a busy signal | **67*number# |
| Unreachable | When the network cannot reach your phone | Calls while the phone is off, out of battery or out of signal | **62*number# |
| Always | Straight away, without ringing your phone | Every call to the line | **21*number# |
| On a schedule | At the times your phone system sets | Evenings, weekends or holidays | Set in your phone system, or switch the always rule by hand |
Carriers and business phone systems can use other codes, an app or a web portal instead, so check your provider's help page first. On GSM networks, ##002# switches off all forwarding.
Forwarding to a traditional answering service or to Asyntai
The rules on your line work the same way for both. What changes is where the call lands and what comes back to you.
| Point | Traditional answering service | Asyntai AI answering service |
|---|---|---|
| Where you forward to | A number that the service gives you | A number in your own Twilio account |
| Who picks up | Operators at the service | An AI agent that says it is an AI assistant, then gives your greeting |
| What the caller can learn | What your script for the service covers | What your website, documents and AI Instructions cover |
| Calls back to your team | Depends on the service | Transfers to the line's transfer number during Escalate to Human hours |
| What you receive | A message, in the format the service uses | A callback request by email with a confirmed number, and the full transcript |
| Billing | Usually by the minute or per call | A monthly plan with included voice minutes; Twilio bills the number and call minutes |
Your phone provider may charge for forwarded calls; check your plan. Twilio rates are on the Twilio voice pricing page.
Test every rule you switch on
A forwarding rule that looks right in a settings screen can still behave differently on a real call. Use a second phone and go through each case once.
- No answer: call your business number and let it ring. Check that the agent picks up after your delay, and that your carrier's voicemail does not answer first.
- Busy: call while your line is in use, and check that the second call reaches the agent.
- Unreachable: put your phone in airplane mode and call it. The agent should answer.
- Transfer: ask the agent for a person during your Escalate to Human hours. Answer once, then let it ring out once, and check that the caller comes back to the agent after 20 seconds.
- Follow-up: leave a callback request, then check your escalation email and the transcript in the dashboard.
Call forwarding answering service: setup questions
For anyone who wants to keep their number and send some, or all, of its calls to the AI agent.
What is a call forwarding answering service?
It is an answering service that receives your calls through call forwarding on your own line. You keep your number, and the rules you switch on send calls to the service. With Asyntai, the destination is a number in your own Twilio account, where the AI agent answers.
Which forwarding rule should I start with?
A simple start is the no-answer rule: your team keeps every call it can take, and the agent answers the rest. Add the busy rule for overflow, and the always rule for evenings or holidays when you are sure of the answers.
Where do I switch call forwarding on?
On your phone line, not in Asyntai. On a mobile it is usually in the phone's call settings or set with carrier codes. On a business phone system, it is in the admin settings or your provider's portal. Point each rule at your Twilio number.
How long should the no-answer delay be?
If the phone that forwards is also the transfer number, more than 20 seconds, so a transfer you miss returns to the agent. Otherwise choose what suits your team: a shorter delay sends calls to the agent sooner.
Does forwarding take the place of my voicemail?
Often, yes. On many mobile lines the carrier's voicemail sits on the same no-answer, busy and unreachable rules, so pointing those rules at the Twilio number puts the agent where voicemail used to be. Test it, as described above.
Does the agent behave differently for each rule?
The agent answers every forwarded call the same way, from your content. What changes with the time is the transfer: inside your Escalate to Human hours a caller who asks for a person is put through, and outside them the agent takes a callback request.
What do forwarded calls cost?
The agent's time comes from your plan's voice minutes: 200 a month on Standard and 1,500 on Pro. Twilio bills the number and the call minutes on your account, and your current provider may charge for forwarding. See answering service cost for a way to estimate your minutes.
How do I stop forwarding for a while?
Switch the rules off on your line. On GSM mobiles, ##002# clears them all. You can also switch the number off in Asyntai, which declines calls with a short message, or remove it, which clears its webhook.
Setting up call forwarding to an AI answering service
A typical way for an answering service, human or AI, to receive your calls is call forwarding on your own line. You keep the number that is on your website and your signs. Your line sends some of its calls to another number, and the service answers there. With Asyntai, that other number sits in your own Twilio account and the AI agent answers it. The quality of the setup depends on the rules you choose, so this page goes through them one at a time, then covers the transfer loop and a test plan.
The no-answer rule is the most common place to start. Your phone rings as it always has. If nobody picks up within the delay you set, the network sends the call on to the Twilio number, and the agent takes it. Your team loses no calls it could have answered, and callers who would have heard a ringing phone or a mailbox reach an agent that can answer their question. If your mailbox answers after a set number of rings today, it may sit on this same rule, and a new destination replaces it. On GSM networks the delay can usually be set between 5 and 30 seconds.
The busy rule sends a call on when your line is already in use. It turns the answering service into overflow: while one customer talks to your team, the next caller talks to the agent instead of hearing a busy signal. How this rule behaves with call waiting depends on your provider, so ask, or test it. The unreachable rule covers the moments when the network cannot find your phone at all: no signal, a dead battery, airplane mode, or a phone switched off for the night. Those calls would otherwise end in a network announcement or a mailbox.
The always rule sends every call on at once, and your own phone does not ring. It suits a day you are closed, a holiday week, or a line where you want the agent to answer first. A schedule is the same idea switched by the clock. Some business phone systems can forward by time of day, so calls go to the agent after closing and come back to the office in the morning. On a line without that feature, switch the always rule on when you close and off when you open. Keep in mind that Asyntai has its own clock as well: the Escalate to Human hours decide whether a caller who asks for a person is transferred or leaves a callback request.
Transfers are where forwarding needs care. When a caller asks for a person in your hours, the agent rings the transfer number of that line for up to 20 seconds. Your phone shows the caller's own number. If nobody answers, or the line is busy, the caller comes back to the agent, which apologizes and takes a callback request. Problems start when the transfer number is the same phone that forwards to the Twilio number. If that phone's no-answer delay is shorter than 20 seconds, the transfer is forwarded on to the Twilio number before it can time out, and the call loops back into the agent. Set the delay to more than 20 seconds, for example 25 or 30. The busy, unreachable and always rules act without a delay, so if the transfer phone uses any of them, give the line a different transfer number.
Take a boarding kennel as an example. The front desk line rings in the office from 7 am to 7 pm. A no-answer rule at 25 seconds and a busy rule send missed calls to the agent during the day, and the office phone system switches to always-forwarding at 7 pm. The agent answers questions about vaccine requirements and pick-up times from the kennel's documents, and takes callback requests for holiday stays, as the kennel's rule tells it to. Transfers go to the kennel manager's mobile, which has no forwarding of its own, so an owner who asks how their dog is doing reaches the manager or comes back to the agent after 20 seconds.
For the caller, the number stays the same. They dial the number they know, and when one of your rules sends the call on, they hear the agent say it is an AI assistant, then your greeting, and get a reply within a second or two of speaking. Test before customers rely on it, using a second phone. Let a call ring out and check that the agent answers after your delay, not your old mailbox. Call while the line is busy. Put the phone in airplane mode and call again. Ask the agent for a person, answer once, and let it ring out once. Then leave a callback request and check that it reaches your escalation email, with the transcript in your dashboard. Each test takes a minute and shows you exactly what a caller will hear.
The Asyntai side of the setup is short. Create an account, add your website and documents, write a greeting on the Voice Agent page and make a free test call in the browser. On the Phone Calls page, paste your Twilio Account SID and Auth Token and import the number that will receive the forwarded calls. Add the transfer number and set your hours under Escalation. Phone calls need the Standard plan, with 200 voice minutes and 2 calls at the same time, or Pro, with 1,500 minutes and 5 calls. The Twilio voice guide shows each screen. For a comparison of answering service options in general, see the answering service guide.
Keep your number and forward the calls you choose
Brief the agent, make a test call in your browser, then switch on one forwarding rule and test it before you add the next.