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Description

Learn how to purchase, import, or verify a phone number so your AI agents can make and receive calls.

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Before You Start

In Callin.io, phone numbers are the foundation of your AI communication system.
Without at least one active number, your assistant won’t be able to make or receive calls. You can add numbers in three different ways:
  • Purchase them directly from Callin.io (Twilio-managed).
  • Import them from a provider such as Twilio or Telnyx.
  • Connect your own SIP trunk using BYOC (Bring Your Own Carrier).
Each option has its own advantages depending on your needs. Let’s quickly go through them so you can decide which one fits your setup best.

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Understanding Your Options

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1. Twilio

Twilio is a cloud-based communications platform that offers APIs for calls, messaging, and video.
It’s the simplest and fastest way to start making calls in Callin.io, because everything — from number provisioning to routing — is fully managed by Twilio’s infrastructure. You should choose Twilio if you want:
  • A quick, no-maintenance setup.
  • Built-in reliability with minimal configuration.
  • Global coverage with easy number search and purchase.
When you buy or import a Twilio number, Callin.io automatically connects it for use within the platform — you don’t need to handle SIP credentials or routing manually.

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2. Telnyx

Telnyx is also a cloud communications provider, but it gives you much deeper control over how your calls are routed and connected.
Telnyx provides direct access to its SIP trunking layer, so you can configure call encryption, codecs, and routing rules as you prefer. You should choose Telnyx if you want:
  • Full control over SIP trunks and routing.
  • Advanced technical settings (QoS, codecs, regional routing).
  • A more flexible setup for compliance or enterprise-scale telephony.
Telnyx requires a slightly more technical setup, but once connected, it’s more customizable and can integrate easily with other network systems.

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3. SIP Trunking (BYOC)

SIP trunking stands for Session Initiation Protocol trunking.
It’s a method that allows you to connect your own telecom infrastructure (your carrier) directly to Callin.io.
You can do this using BYOC (Bring Your Own Carrier). Choose this option if:
  • You already have an existing SIP carrier (for example, your own PBX or corporate system).
  • You need to manage your own routing, SBCs, or regional carriers.
  • You want to use Callin.io as a voice automation layer over your current telecom setup.
With BYOC, you’ll manually configure your SIP credentials and routes — ideal for advanced users or telecom teams.

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Step 1. Connect Your Provider Through BYOC

From the left menu, open Telephony → BYOC.
Here you can link your Telnyx account or any other SIP provider.

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If You Use Telnyx

  • Select the Telnyx tab and enter your API Key.
  • Callin.io will automatically retrieve your active numbers (DIDs).
  • Choose which numbers you want to activate.
  • The system will set up the SIP trunk for inbound and outbound calls.
  • Click Start to begin synchronization.
    Once complete, your Telnyx numbers will appear in your account.

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If You Use Another SIP Provider

  • Go to the Other SIP Provider tab.
  • Configure your SIP trunk manually in three parts:
Basic: Set a name and enter your number in E.164 format.
Inbound: Define where inbound calls will be sent (your SBC/FQDN).
Choose TLS or UDP as the transport protocol.
Allow media encryption if your provider supports it.
Outbound: Enter your SIP credentials (SBC address, username, password) and select outbound country permissions. Click Save & Import when done. Note: Make sure your SBC address and credentials are correct; otherwise, your trunk won’t connect.

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Step 2. Add Numbers to Your Account

After connecting a provider, go to Telephony → Numbers.
This section lists all numbers associated with your account. Click + Add Number, then choose how you want to add it.

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Option 1. Purchase Number

Buy a number directly through Callin.io.
These are Twilio-managed numbers and can only be used within the platform. Choose the country, type (local or toll-free), search by area code, and select your preferred number to purchase.

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Option 2. Import From Twilio

If you already have a Twilio account, you can import your existing numbers.
Enter your Account SID and Auth Token, then select which numbers to import. Once imported, Callin.io will link your Twilio numbers automatically.
You can then assign them to your AI agents to start placing and receiving calls.

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Option 3. Add Personal Number

You can also use your personal number (for example, your mobile phone).
These numbers are outbound-only, meaning they can make calls but not receive them. Verification steps:
  1. Enter your phone number.
  2. You’ll receive a verification call.
  3. Enter the code when prompted.
  4. Your number will be verified and added to your account.

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Option 4. Add Telnyx Number

If your Telnyx account is already connected, you can directly import your active numbers.
Select the ones you want and click Import. Telnyx allows more granular control than Twilio, including:
  • Managing your own routing logic.
  • Adjusting codecs and audio encryption.
  • Enabling multi-region redundancy.
This is ideal for technical users or companies that already manage telecom networks.

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Step 3. Verify Your Numbers

Each number card shows its type and provider.
From this view, you can check:
  • Renewal date.
  • Connection type (direct, SIP, Twilio, or Telnyx).
  • Activation status.
Verify that all numbers are active and properly linked.

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Common Issues and Fixes

Can’t make calls: Make sure your number is active and connected to a valid provider.
Personal number not receiving calls: Personal numbers only support outbound calling.
Missing imported numbers: Double-check your API credentials and DID permissions.

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Final Note

Phone numbers are the link between your AI agents and your real customers.
Whether you choose Twilio for simplicity, Telnyx for control, or your own SIP trunk for full customization, once configured, your agents can call, answer, and automate conversations like a real team — only faster, smarter, and more efficient.