docs: add Bitcall SIP trunking integration guide

fern/advanced/sip/sip-bitcall.mdx

@@ -0,0 +1,107 @@
+---
+title: Bitcall SIP integration
+subtitle: Connect a Bitcall SIP trunk to Vapi for outbound calls
+description: Configure a Bitcall SIP trunk with username and password authentication so your Vapi assistants can place outbound calls.
+slug: advanced/sip/bitcall
+---
+
+Connect your Bitcall SIP trunk to Vapi so your assistants can place outbound calls to phone numbers worldwide. Bitcall authenticates with a SIP username, password and domain, so the setup is one SIP trunk credential and one caller ID.
+
+For SIP trunking concepts and network requirements, see the [SIP trunking guide](/advanced/sip/sip-trunk).
+
+<Note>
+Bitcall is outbound-only. It does not provide phone numbers (DIDs), so it cannot route inbound calls to Vapi. Use it for assistants that place calls, such as reminders, surveys and outbound campaigns.
+</Note>
+
+## Prerequisites
+
+Before you begin, make sure you have:
+
+- A [Bitcall account](https://bitcall.io) with a positive balance
+- A Bitcall SIP account (SIP username and password)
+- An outbound caller ID you are allowed to present on calls
+- A Vapi account and assistant
+
+## Bitcall connection details
+
+| Setting | Value |
+| --- | --- |
+| SIP domain | `gateway.bitcall.io` |
+| Port | `5060` |
+| Authentication | SIP username and password |
+
+<Warning>
+Use username and password authentication. Don't set up IP-based (Trusted IP) authentication on your Bitcall SIP account: Vapi places calls from SIP servers shared by many customers, so an IP allowlist can't identify your organization. Also don't set a Trusted IP and SIP credentials on the same Bitcall SIP account, because authentication then fails.
+</Warning>
+
+## Configure outbound calling
+
+<Steps>
+  <Step title="Create a Bitcall SIP trunk credential">
+    In the [Vapi dashboard](https://dashboard.vapi.ai), select your organization name, then go to **Settings → Integrations → SIP Trunk** and click **Configure New SIP Trunk**.
+
+    Configure the credential with your Bitcall SIP account details:
+
+    - **Name:** A descriptive name, such as `Bitcall`
+    - **IP Address / Domain:** `gateway.bitcall.io`
+    - **Username:** Your Bitcall SIP username
+    - **Password:** Your Bitcall SIP password
+
+    Save the credential and note its credential ID.
+  </Step>
+
+  <Step title="Add your outbound caller ID">
+    Vapi needs a phone number resource to use as the caller ID on outbound calls. Because Bitcall doesn't issue phone numbers, this is the caller ID you want to present, not a Bitcall number.
+
+    Go to [Phone Numbers](https://dashboard.vapi.ai/phone-numbers), click **Create Phone Number** and select **BYO SIP Trunk Number**. Enter your caller ID in E.164 format and select the Bitcall credential in the **SIP Trunk Credential** dropdown. Save the phone number.
+  </Step>
+</Steps>
+
+### Configure with the API
+
+You can create the same resources with the API. Get a [Vapi private API key](/security-and-privacy/api-keys), then create the SIP trunk credential:
+
+```bash
+curl -X POST "https://api.vapi.ai/credential" \
+  -H "Content-Type: application/json" \
+  -H "Authorization: Bearer YOUR_VAPI_PRIVATE_KEY" \
+  -d '{
+    "provider": "byo-sip-trunk",
+    "name": "Bitcall",
+    "gateways": [
+      { "ip": "gateway.bitcall.io", "inboundEnabled": false }
+    ],
+    "outboundLeadingPlusEnabled": true,
+    "outboundAuthenticationPlan": {
+      "authUsername": "YOUR_BITCALL_SIP_USERNAME",
+      "authPassword": "YOUR_BITCALL_SIP_PASSWORD"
+    }
+  }'
+```
+
+Then add your caller ID as a phone number, using the `id` returned above:
+
+```bash
+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": "Bitcall caller ID",
+    "number": "YOUR_CALLER_ID",
+    "numberE164CheckEnabled": false,
+    "credentialId": "YOUR_CREDENTIAL_ID"
+  }'
+```
+
+## Test the integration
+
+1. In Vapi, select an assistant and the caller ID phone number you created.
+2. Place a test call to a phone you can answer.
+3. Verify that the call connects and displays the expected caller ID.
+
+## Troubleshooting
+
+- **The call fails with 401 or 403:** Check the SIP username and password, and make sure the Bitcall SIP account doesn't also have a Trusted IP set.
+- **The caller ID is not shown or is replaced:** Caller ID handling depends on the destination country and operator. Present a number you are allowed to use.
+- **A destination can't be reached:** Dial numbers in E.164 format and check that your Bitcall balance covers the call.

fern/docs.yml

@@ -453,6 +453,8 @@ navigation:
                     path: advanced/sip/sip-didww.mdx
                   - page: didlogic
                     path: advanced/sip/sip-didlogic.mdx
+                  - page: Bitcall
+                    path: advanced/sip/sip-bitcall.mdx
                   - page: Zadarma
                     path: advanced/sip/sip-zadarma.mdx
                   - page: Plivo