### Answer Retell AI does not currently offer a feature to block specific external phone numbers from calling your Retell number based on the available documentation. However, Retell does provide geographic restrictions that allow you to restrict which countries can make inbound calls to your phone numbers: [(1) ]() 1. Navigate to Phone Numbers in your Retell dashboard 2. Click on the phone number you want to configure 3. Under Allowed Inbound Countries, add the countries that should be allowed to call this number When configured, calls from countries not on the list will be automatically rejected. You can also configure this via the API:

bash
curl -X PATCH "<https://api.retellai.com/update-phone-number/+14155551234%22> \
 -H "Authorization: Bearer YOUR_API_KEY" \
 -H "Content-Type: application/json" \
 -d '{
 "allowed_inbound_country_list": ["US", "CA", "GB"]
 }'

For blocking specific individual numbers, you would need to handle this on your telephony provider's platform (e.g., Twilio, Telnyx, Vonage) rather than within Retell directly. Check out these potentially useful sources: - [Fraud Protection]() - [Telnyx]() - [Vonage]()

​ To learn more, see the sources I considered: [[1] Fraud Protection](https://docs.retellai.com/reliability/fraud-protection) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.