### Answer --- I'd need more details about what you're experiencing with your inbound calls to give a specific answer. Could you clarify what behavior you're seeing? Here are some common inbound call issues and their causes: No audio/recording/transcript: - Check the

disconnection_reason

field in your call history—common errors include

error_no_audio_received

(Retell hasn't received audio from the telephony side) . [(1) ]() - If using custom SIP trunking, verify your SIP configuration is correct. Agent not using knowledge base on inbound calls (but works on web calls) : - Ensure your agent is published. [(2) ]() - Try setting the agent to "draft" mode in the Phone Numbers tab to ensure both web and phone use the same agent version. Webhook-related issues: - If you have an inbound webhook configured and it fails (after 3 retries) , the system checks if the number has an inbound agent ID set—if not, the call disconnects. [(3) ]() Call not connecting properly: - Verify your phone number configuration and that an inbound agent is assigned. Please share more details (e.g., call ID, error messages, or the specific behavior) so I can help pinpoint the issue.

​ To learn more, see the sources I considered: [[1] Discord message from @xavera23 on 2025-12-10](https://discord.com/channels/1186424376300679209/1294891368505937952/1448138375013077155) [[2] Inbound Calls Not Accessing Knowledge Base (Urgent)](https://discord.com/channels/1186424376300679209/1440295109286428713) [[3] Inbound webhook](https://docs.retellai.com/features/inbound-call-webhook) ​

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

Thanks for the follow-up, @Reetam. I'll get back to you soon.

​ To learn more, see the sources I considered: [[1] Debug call disconnection](https://docs.retellai.com/reliability/debug-call-disconnect) [[2] Get Call](https://docs.retellai.com/api-references/get-call) ​

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

### Answer A zero-duration call with

user_hangup

as the disconnection reason is unusual. While

user_hangup

normally indicates the user ended the call (expected behavior) , a duration of zero seconds suggests the call may not have fully connected or the user hung up immediately. [(1) ]() A few things to check: 1. Verify call status: Use the [Get Call]() API to check the

call_status

field. If it shows

ended

with zero duration, the call technically connected but ended instantly. [(2) ]() 2. Check for

call_started

webhook: When a call does not connect (e.g.,

dial_failed

,

dial_no_answer

,

dial_busy

) , the

call_started

webhook event will not be triggered—only

call_ended

and

call_analyzed

will fire. [(3) ]() 3. Similar reported issue: There's a known scenario where calls made via Twilio are marked as

user_hangup

but disconnect while the agent is speaking. This was reported as not occurring with web calls from the Retell app. [(4) ]() Possible causes: - The caller hung up before the agent could respond - A telephony/SIP configuration issue on the carrier side - The agent's first message had a delay, causing the user to hang up I'd recommend sharing the specific

call_id

with Retell support if this is happening consistently, as the pattern described in may require investigation on the telephony side.

​ To learn more, see the sources I considered: [[1] Debug call disconnection](https://docs.retellai.com/reliability/debug-call-disconnect) [[2] Get Call](https://docs.retellai.com/api-references/get-call) [[3] Webhook Overview](https://docs.retellai.com/features/webhook-overview) [[4] Calls show user hangup but drop while the agent is speaking](https://discord.com/channels/1186424376300679209/1334212011818618961) ​

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

### Answer Based on the thread context, you're experiencing zero-duration inbound calls with

user_hangup

as the disconnection reason. Key points from the documentation: When a call does not connect (like calls with

dial_failed

,

dial_no_answer

,

dial_busy

disconnection reason) , the

call_started

webhook will not be triggered—but

call_ended

and

call_analyzed

webhooks will still fire. [(1) ]() To investigate further, retrieve the full call details:

javascript
import Retell from 'retell-sdk';
const client = new Retell({
  apiKey: 'YOUR_RETELL_API_KEY',
}) ;
const callResponse = await client.call.retrieve('119c3f8e47135a29e65947eeb34cf12d') ;
console.log(callResponse) ;

[(2) ]() Fields to check in the response: -

call_status

— verify if it shows

ended

or

not_connected

-

start_timestamp

and

end_timestamp

— compare these to confirm zero duration -

transcript

or

transcript_object

— see if any audio was exchanged If

call_started

webhook wasn't triggered but

call_ended

was, this indicates the call never fully connected on the telephony side—even though the disconnection reason shows

user_hangup

. [(1) ]() Since this appears to be a recurring pattern, I'd recommend reaching out to Retell support with your specific

call_id

values for investigation: - Visit [Contact Sales]() - Visit [)

​ To learn more, see the sources I considered: [[1] Webhook Overview](https://docs.retellai.com/features/webhook-overview) [[2] Get Call](https://docs.retellai.com/api-references/get-call) ​

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