> ## Documentation Index
> Fetch the complete documentation index at: https://documentation.uponai.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Connect Twilio via SIP Trunking

> Integrate your Twilio numbers with UponAI using elastic SIP trunking.

## Setup Steps

<Steps>
  <Step title="Create Elastic SIP Trunking in Twilio">
    In your Twilio Console, create a new SIP trunk and give it a name.

    **Configure Termination (outbound):**

    * Note the **Termination SIP URI** — you'll use it when importing numbers to UponAI. Use a localized URI near your region for best performance.
    * To allow UponAI's outbound requests, either:
      * Whitelist UponAI's SIP CIDR block: `18.98.16.120/30`
      * OR create auth credentials (username + password) — you'll supply these when importing to UponAI

    **Configure Origination (inbound):**

    * Set the origination SIP URI to: `sip:sip.retellai.com`
  </Step>

  <Step title="Move numbers to your SIP trunk">
    Purchase new numbers or move existing Twilio numbers to the elastic SIP trunk you just created.
  </Step>

  <Step title="Import numbers to UponAI">
    In the UponAI dashboard, import the number by supplying:

    * The **Termination SIP URI** from Step 1
    * Username and password (if you chose credential auth)

    You can also import numbers programmatically via the Import Number API.

    Once imported, the number behaves exactly like a UponAI-purchased number — it appears in your dashboard and can make and receive calls. To remove it, delete it from the dashboard or via the Delete Number API.
  </Step>
</Steps>

## Common Issues

**Inbound works but outbound doesn't:**

* Check the Termination SIP URI for any spaces — remove them
* Use a localized Termination SIP URI near your region
* Double-check your username and credentials. The **username** is different from the friendly name shown in the credential list — verify the actual username, not the display name

**Calling international countries:**

* In Twilio Console, search "geo" to find **Voice Geographic Permissions**
* Select **Elastic SIP Trunking** and enable the countries you want to call

## Phone Number Masking (Caller ID)

Display a verified personal or business number as the caller ID for outbound calls.

<Steps>
  <Step title="Add a verified caller ID">
    1. Go to **Verified Caller IDs** in Twilio Console
    2. Click **Add a new Caller ID**
    3. Enter the phone number, choose a verification method, and click **Verify Number**
    4. Enter the OTP code you receive to complete verification
  </Step>

  <Step title="Configure SIP header rules">
    1. In Twilio Console, navigate to **Elastic SIP Trunking → Trunks → \[your trunk] → Termination**
    2. Scroll to **Header Manipulation** and click **View all SIP header manipulation policies**
    3. Click **Create a policy** and give it a name
    4. Click **+ Add request rule** and configure:
       * **SIP header field:** From number
       * **Action:** Replace with
       * **Value:** Your caller ID in E.164 format (e.g. `+18881230987`)
    5. Click **Add rule**, then **Save policy**
    6. Back on the Termination tab, select your new policy from the dropdown
  </Step>
</Steps>

<Note>
  You need at least one number purchased from Twilio in your SIP trunk for the caller ID to be applied. Test with an outbound call to validate.
</Note>