Troubleshooting Dropped Twilio Voice Calls

When a caller or callee reports an active Twilio call disconnecting unexpectedly, we refer to this as a dropped call. Dropped calls can be caused by a number of factors including connection problems over a specific route, network connectivity issues with one or both ends of the call, long periods of silence, or even certain software problems. This guide is intended to help diagnose any issues due to dropped calls.

Check for Twilio Incidents

Check the Twilio Status Page to see if there is an active incident, or an incident during the timeframe you reported issues, that could be causing your issues. For full details, please see Checking Twilio Service and API Status with the Status Page.

No incidents are listed that may be affecting calls: If you don't see an incident posted that may affect calls, then there is likely an issue elsewhere. Continue reading for additional troubleshooting.

An incident may be affecting calls: If you see an incident posted that may affect outgoing Twilio calls, please monitor the status, and then test again once the incident is resolved.

Identify the Issue

Attempt to ascertain the full details surrounding this issue:

  • Does the call log show any Debug Events?
  • Did the call drop after a long silence, mute, or hold? Our system automatically ends calls after 60 seconds of silence.
  • Does this issue occur at the same time each call?
  • Is your TwiML URL or Application SID sending <Hangup> TwiML?
  • For Elastic SIP Trunking or SIP Domain calls, which side is sending the BYE responses in the Packet Capture?
  • For Voice Insights users, do which side is Hanging up?
  • Did you or your application update the call status via an API request and end it?
  • Does this issue only occur with specific phone numbers or number types (landline, mobile, VoIP, etc.)?
  • Does this issue only occur when calling or receiving calls from a specific region or country?
  • Do other callers/callees report similar issues?

Once you are able to answer these questions, continue reading for additional troubleshooting.

Attempt to Replicate the Issue

Attempt another test call or two between the same phone numbers, and then try using the same Twilio phone number with different caller/callee phone numbers. The goal is to determine if this was a one-off, if the issue is limited to specific phone numbers or service providers, or if there may be a larger issue that requires investigation.

Calls are always dropped: If you see call drops on all calls in the same direction (to or from) with your Twilio phone number, there's likely an issue elsewhere. Please review the troubleshooting in the previous section.

Some calls are dropped: If you are able to replicate the call drop issues only some of the time on calls in the same direction, check for any patterns:

  • If calls are dropped only from incoming callers using a specific service provider (or a small group of providers), then escalate to the caller's service provider.
  • If calls are dropped only on outgoing call to a specific service provider (or a small group of providers), then continue reading for additional troubleshooting.
  • If no pattern can be found, collect additional examples, and then continue reading for additional troubleshooting.

Unable to replicate this issue: If you are unable to replicate the call drop issues, it's unlikely we will be able to address this report. Continue to monitor, and restart troubleshooting as needed if additional reports are received.

Escalate to Twilio Support

If you can rule out all of the above issues, Twilio's Support team can help investigate what went wrong. Please collect 3 or more examples of calls to or from the same Twilio phone number that have reported call drops from the last 24 hours, and include the following information:

  • Call SIDs
  • Description of call drop issues
  • Variance of issues
  • Frequency of issues
  • Replication pattern

When you have collected this information, please share it with our Support team.

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