Twilio: send only one hangup command

CHANGELOG.md

@@ -13,6 +13,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   the Telnyx call when an `EndFrame` or `CancelFrame` is received. It is
   enabled by default and is configurable via the `auto_hang_up` `InputParam`.
 
+### Fixed
+
+- Fixed an issue where `TwilioFrameSerializer` would send two hang up commands:
+  one for the `EndFrame` and one for the `CancelFrame`.
+
 ## [0.0.64] - 2025-04-22
 
 ### Added

src/pipecat/serializers/twilio.py

@@ -90,6 +90,7 @@ class TwilioFrameSerializer(FrameSerializer):
         self._sample_rate = 0  # Pipeline input rate
 
         self._resampler = create_default_resampler()
+        self._hangup_attempted = False
 
     @property
     def type(self) -> FrameSerializerType:
@@ -120,7 +121,12 @@ class TwilioFrameSerializer(FrameSerializer):
         Returns:
             Serialized data as string or bytes, or None if the frame isn't handled.
         """
-        if self._params.auto_hang_up and isinstance(frame, (EndFrame, CancelFrame)):
+        if (
+            self._params.auto_hang_up
+            and not self._hangup_attempted
+            and isinstance(frame, (EndFrame, CancelFrame))
+        ):
+            self._hangup_attempted = True
             await self._hang_up_call()
             return None
         elif isinstance(frame, StartInterruptionFrame):