I have been wondering about this about the personal questions aspect. I believe my solution of informing them it's an AI may reduce that issue, though you could also do the fancy and have the AI post either the message on your phone screen so you can answer, or just have it reply "I don't know". If creating the appointment then failed the AI could go back to the user and say "I couldn't book the appointment because...", allowing the user to then give more detailed instructions.
We're at the precipice of incredible technology here, so who knows where it will go.
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