How to connect Twilio to an AI voice agent: numbers, carriers and SIP basics

To connect Twilio to an AI voice agent, you buy or port a number in your Twilio account, link that account to your Purple Voice workspace, and assign the number to an agent for inbound calls or a campaign for outbound ones. The number stays yours; the platform simply makes and answers calls through it.

The tricky parts are not the clicks. They are knowing what a carrier is doing behind the number, which country rules apply, and why a perfectly built agent can still go unanswered if the number looks wrong. This guide explains the pieces in plain language.

Why Purple Voice runs on your own numbers

Purple Voice supports Twilio, Plivo and SuperPhone, and calls go out and come in on numbers you control. That has three practical benefits:

• You own the identity. If you ever change tools, the number and its reputation stay with you.
• You see the real costs. Phone-number rental and call charges are billed by the provider, not folded into a platform fee.
• You can choose by country. Different providers are stronger in different regions, so you pick what fits where your leads are.

The trade-off is that you carry the carrier relationship. You set up the account, keep it funded and deal with any registration the country requires.

The three layers behind a phone call

It helps to picture three layers.

1. The number. The identity your lead sees and dials, such as +44 or +1 numbers rented from a provider.
2. The carrier network. Twilio, Plivo or SuperPhone sits between the public phone network and your software. It routes the call and bills for minutes.
3. The agent. The AI that speaks. It is attached to the carrier through a standard connection, so a call to your number ends up in a conversation with your agent. How that conversation works internally is covered in how AI voice agents work.

When something breaks, it is almost always one of the first two layers, not the AI.

SIP basics, at a high level

SIP, the Session Initiation Protocol, is the common language phone systems use to start, manage and end calls over the internet. When a call to your number arrives, the carrier uses SIP to tell connected software "a call has come in, here are the details", and the software replies and takes over the audio.

You do not need to configure SIP by hand to use the dashboard. It is worth knowing the term because you will meet it in carrier documentation, in error messages and in any conversation about moving numbers between providers. If you ever hear "SIP trunk", it means a connection that carries many calls between a carrier and a system, a bit like a bundle of phone lines made of software.

Step by step: getting a number ready

The exact screens differ by provider, but the sequence is stable.

1. Create and fund the provider account

Open an account with the carrier you have chosen and add credit. Calls and number rental are charged to you, so keep an eye on balance, especially during a campaign.

2. Get a number

Buy a new number in the country and type you need. Local numbers usually feel more familiar to leads than unfamiliar ones. If you already have a business number, you can often port it, but porting takes time and has paperwork, so do not leave it to the day you want to launch.

3. Handle registration where required

Some countries and number types require business or identity registration before you can use them for outbound calling. Requirements change, so read the current rules from your carrier and your regulator rather than relying on a blog post, this one included.

4. Link the account in Purple Voice

In the Phone numbers area of the dashboard, connect the provider account and select the number. Plan limits: Free and Basic include one number, Pro supports unlimited numbers.

5. Assign the number

Attach the number to an agent for inbound calls, or select it in a campaign for outbound ones. See how to launch an AI calling campaign for the campaign side.

6. Make a test call

Ring the number from your own mobile and talk to the agent, then use the agent's test-call feature to have it call you. Both directions should work before real leads are involved. The full pre-launch routine is in test your AI voice agent.

Choosing between Twilio, Plivo and SuperPhone

There is no universal winner. Compare on what matters for your case:

Question	Why it matters
Do they offer numbers in your target countries?	Coverage gaps can rule out a provider
What does a minute cost for your destinations?	Prices differ by country and call type
What registration do they require?	Some markets add steps before outbound use
How is support when something breaks?	Matters most during a live campaign
Do you already have an account?	Reusing one is faster than starting over

If you already use one of these, start there. Switching because of a small price difference rarely pays off in your first month.

Why calls get ignored or flagged

A well-configured number still faces filtering. Carriers and phone apps score numbers on factors such as call volume, how often calls are answered, complaints and registration status. You cannot control the labels, but you can avoid the habits that trigger them:

• Do not blast a large list from a brand-new number on day one. Ramp up.
• Call in sensible hours for your leads' time zone.
• Keep lists clean and remove anyone who asks to stop, as in do-not-call lists and dialer hygiene.
• Make sure the agent introduces itself clearly. Disclose AI on calls covers wording and timing.
• Use a number in the country you are calling where possible.

Be honest with yourself about limits: no platform can guarantee how a carrier will label or deliver a call.

Inbound versus outbound on the same number

One number can do both, but think about what each direction needs. Inbound callers expect a published line that answers every time; outbound leads expect the number to match whoever contacted them. If volume grows, separate numbers keep the two clean, and Pro removes the number limit for that reason.

Try it

Purple Voice works on your own Twilio, Plivo or SuperPhone numbers, and the Free plan includes one agent and one number with 100 minutes a month, no card needed. Start at voice.purplerocket.co, connect your provider, and make a test call to your own phone. Provider charges are billed by the provider, and platform plans are on the pricing page.