haring our journey building an overflow receptionist in case it helps others. What we were trying to achieve: An inbound assistant (Sienna) that answers calls, transfers to a department, and if no one answers after 15 seconds the call returns to Sienna automatically so she can take the caller's details — all in one single call session so context is preserved. What we tried first: Set Transfer Mode to Warm Transfer Experimental with endCallEnabled set to false. The call was not returning to Sienna at all — it just died after no answer. What VAPI bot recommended: Use assistant-based warm transfer by adding a transferAssistant block inside the destination config with maxDurationSeconds set to 15. We updated the tool via the VAPI API using a PATCH request since the dashboard UI doesn't allow editing the JSON directly. Result after that fix: The call now returns to Sienna after 15 seconds which is exactly what we needed. Remaining problem: Before Sienna continues the conversation, VAPI is automatically saying "could not transfer the call." We removed the fallbackPlan completely from the JSON but the message is still playing. It seems VAPI is hardcoding it internally. How can I solve these problem

Please share your call id/org id so we can look into it.