### Answer The voice agent changing mid-call is typically caused by the fallback voice system activating when the primary TTS provider experiences an outage [(1) ]() [(2) ]() . When you configure a voice agent, you can set

fallback_voice_ids

- a list of backup voices from different TTS providers . The system automatically switches to these fallback voices in order when the primary voice's TTS provider has issues . To prevent unexpected voice changes: 1. Remove fallback voices - Set

fallback_voice_ids

to

null

to disable voice fallback entirely 2. Check your configuration - Verify what fallback voices are currently assigned to your agent The fallback system requires that the voice ID and fallback voice IDs must be from different TTS providers . If the first fallback is also experiencing an outage, the system moves to the next one in the list . If you're experiencing this without having configured fallback voices, or if the issue persists after removing them, I'd recommend checking your agent configuration via the API or dashboard to confirm your current voice settings.

​ To learn more, see the sources I considered: [[1] Update Voice Agent](https://docs.retellai.com/api-references/update-agent) [[2] Create Voice Agent](https://docs.retellai.com/api-references/create-agent) ​

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