It's 8:40 on a Tuesday evening. A dental clinic is closed, the front desk is dark, and the phone rings. A new patient wants to book a cleaning. Normally that call dies in voicemail, and the patient calls the next clinic on the list. We wanted to see what would happen if something picked up instead. So we built one — an AI that answers the phone, has a real conversation, and books the appointment. We named her Ava. Going in, we assumed the challenge would be making her sound human. That tur...