i feel like vapi inbuilt functions can be little inconsistent maybe builld your own custom function to end call. Should be possible from vapi if you can filter the call sid from twilio by looking at the callers number. Also feel like you might have firstmessage enabled and are using the first message column. Usually if I want vapi to run a function as soon as the call starts I make sure to disable first message. Feel like with first message enabled VAPI will just repeat the static message you put there and then wont follow the prompt or do anytype of action until the caller responds