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Prerequisites

Before you begin, ensure you have:
  1. An active phone number on your Wavix account. If you need to purchase one, see our guide on how to buy a phone number.
  2. A SIP trunk (How to create a SIP trunk).

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Receive calls with Wavix and Vapi

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Create SIP trunk credentials in Vapi

  1. Sign in to your Vapi account.
  2. Go to API Keys.
  3. Copy your Private Key.
  4. Run the POST request below using your favorite tool, such as Postman or terminal.
curl -L 'https://api.vapi.ai/credential' \
-H 'Content-Type: application/json' \
-H 'Authorization: Bearer YOUR_VAPI_PRIVATE_KEY' \
-d '{
    "provider": "byo-sip-trunk",
    "name": "Wavix",
    "gateways": [
        {
            "ip": "95.211.82.14"
        },
        {
            "ip": "209.58.144.243"
        },
        {
            "ip": "173.234.106.26"
        },
        {
            "ip": "23.108.101.90"
        }

    ],
    "outboundLeadingPlusEnabled": true,
    "outboundAuthenticationPlan": {
        "authUsername": "YOUR_SIP_TRUNK_ID",
        "authPassword": "YOUR_SIP_TRUNK_PASSWORD"
    }
}'
  • Replace YOUR_SIP_TRUNK_ID and YOUR_SIP_TRUNK_PASSWORD with the SIP trunk credentials configured in the Wavix portal.
  • Replace YOUR_VAPI_PRIVATE_KEY with your Vapi Private Key.
Make sure you list all Wavix regional gateway IP addresses in the ‘gateways’ array. Failing to do so may result in your calls being rejected with 401 Unauthorized error. A full list of regional gateways is shown at the bottom of the Trunks page in the Wavix portal.
If successful, the response will contain the SIP trunk credentials id. Copy it for later use. 
{
    "id": "00000000-c5c6-4f68-bb6d-000000000000",
    "orgId": "00000000-b275-4b33-9dd2-000000000000",
    "provider": "byo-sip-trunk",
    "createdAt": "2025-10-13T10:56:17.439Z",
    "updatedAt": "2025-10-13T10:56:17.439Z",
    "gateways": [
    ],
    "name": "Wavix",
    "outboundLeadingPlusEnabled": true
}
Learn more about Vapi SIP trunks in the Vapi SIP trunk documentation.

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Associate a phone number with the SIP trunk

To link your Wavix phone number to the SIP trunk credential in Vapi, you need to create a Phone Number resource. Run the POST request below using your favorite tool, such as Postman or terminal. 
curl -X POST "https://api.vapi.ai/phone-number" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_VAPI_PRIVATE_KEY" \
  -d '{
    "provider": "byo-phone-number",
    "name": "Wavix Number",
    "number": "YOUR_WAVIX_PHONE_NUMBER",
    "numberE164CheckEnabled": false,
    "credentialId": "YOUR_VAPI_CREDENTIAL_ID"
  }'
  • Replace YOUR_WAVIX_PHONE_NUMBER with a number on your Wavix account and YOUR_VAPI_CREDENTIAL_ID with your Vapi SIP trunk credentials created earlier.
  • Replace YOUR_VAPI_PRIVATE_KEY with your Vapi Private Key.
Make sure YOUR_WAVIX_PHONE_NUMBER contains the leading ’+’ sign, i.e., +61290597521.
If successful, the phone number will appear in your Vapi account. Phone numbers in your Vapi account To assign an AI assistant to the phone number:
  1. Sign in to your Vapi account.
  2. Go to Phone Numbers.
  3. Scroll down to Inbound Settings and associate an assistant with the number.

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Setup inbound call routing on Wavix

Wavix can route inbound calls to a SIP trunk on the platform, SIP URI, or forward them to a phone number. Vapi requires calls to be routed to a SIP URI. To route calls to your Wavix number to the Vapi SIP URI:
  1. In Wavix, open Numbers & trunks → My numbers.
  2. Select your number by clicking the ⋯ menu → Edit number.
  3. Set the inbound call destination type to SIP URI, and enter the destination in the format of:
[did]@YOUR_VAPI_CREDENTIAL_ID.sip.vapi.ai
In the example above, it would be: 
[did]@00000000-c5c6-4f68-bb6d-000000000000.sip.vapi.ai
  1. Save your changes.
Now, all calls to your Wavix number are routed to your Vapi AI assistant.

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Place calls with Wavix and Vapi

To place an outbound call, you’ll need a Vapi Assistant ID and Vapi Phone Number ID.
  1. In Vapi, open Assistants.
  2. Select an assistant you want to use and copy the assistant ID. Assistants in your Vapi account
  1. In Vapi, open Phone Numbers.
  2. Select a number you want to use as Caller ID and copy the number ID. Phone numbers in your Vapi account
You can place outbound calls with Vapi using the API. Run the POST request below using your favorite tool, such as Postman or terminal. 
curl -L 'https://api.vapi.ai/call/phone' \
-H 'Content-Type: application/json' \
-H 'Authorization: Bearer YOUR_VAPI_PRIVATE_KEY' \
-d '{
  "assistantId": "YOUR_VAPI_ASSISTANT_ID",
  "customer": {
    "number": "DESTINATION_NUMBER",
    "numberE164CheckEnabled": true
  },
  "phoneNumberId": "YOUR_VAPI_NUMBER_ID"
}
'
  • Replace YOUR_VAPI_ASSISTANT_ID with your Vapi Assistant ID and YOUR_VAPI_NUMBER_ID with your Vapi Phone Number ID.
  • Replace YOUR_VAPI_PRIVATE_KEY with your Vapi Private Key.
  • Replace the DESTINATION_NUMBER with a phone number you want to call. Make sure the phone number is provided in the international E.164 format with or without the leading + sign.
If successful, the Vapi places a call to the destination number.
Learn more about Vapi outbound calls in the Vapi outbound calling documentation.

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Transfer calls between Vapi and Wavix

Wavix supports using the SIP REFER command. To transfer a call, you need two Wavix numbers, one for an active call and one to receive the transferred call. Make sure inbound call routing is set up on the second number. To enable call transfers with Vapi, you’ll need:
  1. Create and configure a Transfer Call tool.
  2. Associate the tool with your Vapi assistant.

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Configure Transfer Call

To configure the Transfer Call tool:
  1. In your Vapi account, select Tools.
  2. Select + Create Tool, choose Transfer Call, and enter a name for the tool.
  3. Under Destinations, select + Add Destination, then choose SIP.
  4. In the SIP URI field, enter the address in this format:[YOUR_WAVIX_NUMBER]@[WAVIX_SIP_GATEWAY]. Example: sip:14067704205@us.wavix.net.
  5. In the Message to Customer field, enter the message to speak to the customer before the transfer.
  6. Provide additional details to help the AI decide when to use this destination.
  7. In Transfer Mode, make sure Blind Transfer is selected.
  8. Select Save.
Replace YOUR_WAVIX_NUMBER with your Wavix number and WAVIX_SIP_GATEWAY with one of Wavix’s SIP gateways.
Choose the primary Wavix gateway with the lowest ping from your location. A full list of regional gateways is shown at the bottom of the Trunks page in the Wavix Customer portal.
Configure a Transfer Call tool in your Vapi account
Learn more about Vapi call transfer in the Vapi call forwarding documentation.

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Troubleshooting

  • 603 Declined can occur if the destination’s per‑minute rate is higher than your account’s Max call rate (check the value on the Trunks page). Contact support@wavix.com to request a change if needed.
  • Wrong number format. Dial the full international E.164 number, e.g. 19085594899 (US) or 4408001218915 (UK). Do not dial local formats like 9085594899. Strip prefixes like 0, 00, or 011 before the dialed number.