It would do that automatically.
Have you had a full call with your bot yet or no?
What you are explaining I did not cover in that video. That was a call coming from the CRM with that information already directly inside of the prompt with custom values.
What you are talking about is the voice assistant having a conversation and simply asking quesitons and remembering the question. That cna be achieved with prompting. Make sure to take a look at the VAPI prompting guide.