Hello! I am trying to create a simple assistant that will ONLY perform the following tasks: * read out a short, pre-defined greeting * allow the user to speak to leave their message * (optional) end the call once the user has stopped leaving their message I want to do this so that users can leave "voicemails" and I can leverage the VAPI call recording features. Problem is that I can't create an assistant without selecting an LLM and no matter how I prompt the LLM I can't seem to keep it from responding to the user and interrupting their "voicemail". Thanks in advance for your help here!