# Caller ID number changing unexpectedly in Retell + Twilio setup

**URL:** <https://community.retellai.com/t/caller-id-number-changing-unexpectedly-in-retell-twilio-setup/824>\
**Category:** Support Help\
**Tags:** telephony\
**Created:** [February 11, 2026, 6:17pm UTC](https://community.retellai.com/t/caller-id-number-changing-unexpectedly-in-retell-twilio-setup/824 "2026-02-11T18:17:03Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![support2](https://yyz2.discourse-cdn.com/flex008/user_avatar/community.retellai.com/support2/32/15_2.png) [@support2](https://community.retellai.com/u/support2)\
**Post date:** [February 11, 2026, 6:17pm UTC](https://community.retellai.com/t/caller-id-number-changing-unexpectedly-in-retell-twilio-setup/824/2 "2026-02-11T18:17:35Z")

</div>

The behavior you’re experiencing—where the caller ID changes to different Brazilian numbers instead of your registered +1 number—is not standard Retell AI behavior and indicates a configuration issue.

**Phone Number Masking Configuration**

Retell AI supports phone number masking through Twilio’s verified caller ID feature[(1)](https://docs.retellai.com/deploy/twilio). If you want your personal phone number or trusted business number to display to the callee, you need to configure verified phone numbers in Twilio to serve as the caller ID[(1)](https://docs.retellai.com/deploy/twilio).

To set this up properly:

1. Go to the Verified Caller IDs page in Twilio[(1)](https://docs.retellai.com/deploy/twilio)
2. Click “Add a new Caller ID”[(1)](https://docs.retellai.com/deploy/twilio)
3. Enter the desired phone number to verify and select the verification method[(1)](https://docs.retellai.com/deploy/twilio)
4. The number will receive an OTP Authentication code for verification[(1)](https://docs.retellai.com/deploy/twilio)
5. Once verified, configure SIP Header Rules to display the caller ID[(1)](https://docs.retellai.com/deploy/twilio)

**SIP Header Manipulation for Caller ID**

In the Twilio Console, navigate to Elastic SIP Trunking → Trunks → [your trunk] → Termination[(1)](https://docs.retellai.com/deploy/twilio). Under Header Manipulation, create a policy with the following settings[(1)](https://docs.retellai.com/deploy/twilio):

- **SIP header field** : From number[(1)](https://docs.retellai.com/deploy/twilio)
- **Action** : Replace with[(1)](https://docs.retellai.com/deploy/twilio)
- **Value** : Your caller ID in E.164 format (e.g. +18881230987)[(1)](https://docs.retellai.com/deploy/twilio)

After creating the policy, select it from the dropdown in the Termination tab[(1)](https://docs.retellai.com/deploy/twilio). Any number imported from this Twilio trunk into your Retell account will then use your verified caller ID[(1)](https://docs.retellai.com/deploy/twilio).

**Regional Considerations for Brazil**

Based on community reports, there may be carrier-specific restrictions when calling Brazilian numbers from international caller IDs[(2)](https://discord.com/channels/1186424376300679209/1430255602814287964). Some Brazilian carriers block or restrict calls to certain number ranges when originating from outside specific metropolitan areas[(2)](https://discord.com/channels/1186424376300679209/1430255602814287964). The rotating Brazilian numbers (+55) you’re seeing suggest that Twilio may be attempting to route calls through local gateways, which could explain the changing caller IDs.

**Recommended Actions**

1. Verify your SIP Header Manipulation policy is correctly configured in Twilio[(1)](https://docs.retellai.com/deploy/twilio)
2. Ensure you have at least one number purchased from Twilio in your SIP trunk for the caller ID to be applied[(1)](https://docs.retellai.com/deploy/twilio)
3. Check your Twilio logs for any error codes that might indicate routing issues[(3)](https://community.retellai.com/t/problem-with-outbounding-call/514)
4. Contact Twilio support to understand any restrictions on your specific phone number configuration[(2)](https://discord.com/channels/1186424376300679209/1430255602814287964)

The fact that it worked initially but changed after updating your agent script suggests the issue may be related to your Twilio trunk configuration rather than the Retell agent itself.

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_[View the full topic](https://community.retellai.com/t/caller-id-number-changing-unexpectedly-in-retell-twilio-setup/824)._