Configure an Atom number in Vapi

Voice

Connect an Atom Voice Service and its assigned telephone number to a Vapi assistant so it can receive and make calls. This guide uses the Vapi dashboard and SIP registration with the Atom service's username and password.

Before you begin

Make sure you have:

Access to create and manage a Voice Service in the Atomic portal.
An Atom telephone number assigned to that Voice Service.
Access to your Vapi organisation and the assistant that will handle calls.
The SIP Account and VOIP Password for the Atom Voice Service.
An external phone you can use for the inbound and outbound tests.

Keep your password secure: Store the SIP password securely. Do not include it in screenshots, support tickets or chat messages.

If you already have a Voice Service and assigned number for Vapi, continue to Configure the SIP connection.

Create the Atom Voice Service

Navigate: Services > Voice in the Atomic portal.

Step 1: Sign in to the Atomic portal.

Step 2: In the sidebar, open Services then select Voice.

Open Voice from the Services menu in Atomic

Step 3: Select Add Service.

Select Add Service to create a voice service

Step 4: Select the customer that will own the service.

Select the customer and SIP Trunk service type

If the customer does not exist, follow Create a customer first.

Step 5: Select SIP Trunk as the Voice Service type and choose the required service plan.

Step 6: Give the service a clear name that identifies its Vapi use, such as Acme Voice - Vapi.

Step 7: Save the service.

Order and assign a number

Step 1: Follow the number-ordering guide to order a number through Number Request.

Step 2: Make sure the ordered number is assigned to the Voice Service you created for Vapi.

Step 3: Record the assigned number with its country code. You will use this telephone number when adding it to Vapi.

Use the assigned telephone number: The number you add to Vapi is the telephone number assigned to the Voice Service, separate from its service identifier or SIP Account.

Configure the SIP connection

Navigate: Voice Service Manage > Connections > SIP End Point.

Step 1: Return to the Voice Services list, find the service you created for Vapi and select Manage.

Step 2: Select Connections then open SIP End Point.

Service configuration on Connections > SIP End Point, with the SIP account settings and enable togg…

Step 3: Turn on Enable SIP Account.

Step 4: Record the SIP Account. Use this value wherever Vapi requests the username or registration username.

Step 5: Enter a VOIP Password for the service and enter it again in the confirmation field.

Step 6: Select Update and store the credentials securely.

The registration domain used in this setup is sip3.atomcomm.com.

Add the SIP trunk in Vapi

Navigate: Settings > Integrations > Phone Number Providers > SIP Trunk.

Step 1: Sign in to Vapi and select the organisation you want to configure.

Step 2: Select Integrations in the left navigation.

Vapi Integrations page with the SIP Trunk provider option highlighted.

Step 3: Under Phone Number Providers, select SIP Trunk then select Configure New SIP Trunk.

SIP Trunk dialog with the Configure New SIP Trunk button highlighted in Vapi’s phone number settings

Step 4: Enter a clear name, such as Acme Voice - Vapi.

Vapi SIP trunk setup with the name field and Gateway #1 configuration highlighted

Step 5: Under Gateway Configuration, enter these settings for Gateway #1:

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IP Address / Domain	`52.65.130.216`
Port	`5060`
Netmask	`32`
Outbound Protocol	`UDP`
Allow inbound calls	On
Allow outbound calls	On
Enable options ping	Off

Leave other gateway settings at their defaults.

Step 6: Under Authentication (Optional), enter these settings:

SIP trunk setup with the Authentication (Optional) fields highlighted.

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Username	The Atom service's SIP Account
Password	The service's VOIP Password
Use SIP Registration	On
Domain	`sip3.atomcomm.com`
Registration Username	The same SIP Account used for Username
Realm	`sip3.atomcomm.com`
Use public IP in Contact header	Off

Step 7: Under Advanced Settings, leave Enable leading plus for outbound calls and Use Cluster SIP set to Off. Keep other options at their defaults.

Vapi SIP Trunk dialog with Advanced Settings and the Save SIP Trunk button highlighted

Step 8: Select Save SIP Trunk.

Add the Atom number to Vapi

Navigate: Phone Numbers in Vapi.

Step 1: Open Phone Numbers.

Vapi Phone Numbers page with the menu item and Create Phone Number button highlighted

Step 2: Select Create Phone Number then choose BYO SIP Trunk Number.

Vapi phone number options with BYO SIP Trunk Number selected and the phone number field displayed

Step 3: Enter the telephone number assigned to your Atom Voice Service in E.164 international format.

Vapi BYO SIP trunk dialog with the Atom number entered in the Phone Number field in E.164 format

Number format: Include the leading +, country code, area code and subscriber number without spaces. Use your assigned Atom telephone number.

Step 4: In Label, enter a clear name such as Acme Voice - Vapi.

Step 5: In SIP Trunk Credential, select the trunk you created for the Atom service then select Import SIP Phone Number.

Step 6: On the imported number page, under Inbound Settings, select the assistant that will answer calls to this number.

Inbound Settings with Acme Voice assistant selected and Save highlighted

Step 7: Select Save to save the assistant assignment.

Set the number options in Atomic

Step 1: Return to the Atom Voice Service you created for Vapi and open its assigned number's Edit DID page.

Step 2: In Incoming Connection, select Sip End Point.

DID edit dialog with Sip End Point selected and Number Format set to +E.164

Step 3: Set Number Format to +E.164.

Step 4: Enable Forward DID in URI.

Step 5: Enter a clear DID Label that identifies its Vapi use.

Step 6: Select Save to save the DID settings.

This setup uses the SIP registration configured above. A separate SIP Incoming Trunk is not part of this procedure.

Verify inbound calling

Step 1: Call the assigned Atom telephone number from an external phone.

Step 2: In Vapi, open Logs then select Calls.

Vapi Logs page with the Calls tab selected and no call logs available yet

Step 3: Find the test call and confirm that the assistant assigned to the number answers.

Step 4: Check that you can hear the assistant and that the assistant can hear you.

If the call does not appear, check that Allow inbound calls is On, the DID options were saved and the correct assistant is assigned to the imported number.

Verify outbound calling

Step 1: In Vapi, open Phone Numbers and select the imported Atom number.

Step 2: Select Test.

Vapi phone number screen with the Test panel open and Single Number selected

Step 3: Choose Single Number.

Step 4: Enter an external telephone number you control in international format and select the assistant for the test.

Step 5: Select Call and answer the test call.

Step 6: Confirm that the call connects, audio works in both directions and the caller ID is the Atom number assigned to the Voice Service.

Use a different caller ID only if Atom has approved it. If outbound dialling fails, confirm the required destination format with Atom before changing Enable leading plus for outbound calls.

Troubleshooting

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Vapi cannot save the trunk	Check the gateway IP, port `5060`, netmask `32` and selected Vapi organisation and region
No inbound call in Vapi	Check the assigned number, saved DID options, Allow inbound calls and assistant selection
Outbound call returns 401 or 407	Check the SIP Account, VOIP Password, registration username, domain and realm
Outbound call returns 403	Check the Atom service's destination permissions, assigned number and approved caller ID
Call connects with one-way or no audio	Ask the providers to check media connectivity and compatible audio codecs

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