You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. Can you please tell me how may I assist you?

USER: I'm Melissa Martinez.

ASSISTANT: Ok.

USER: Due to an emergency in my sister's home I would like to change my existing reservation, so could you please book a ticket from DEN to OAK?

ASSISTANT: Ok, wait a minute.

USER: Sure.

ASSISTANT: Sorry to say, no reservation found on your details to change your existing reservation.

USER: That's ok, thank you.

ASSISTANT: Thank you for contacting us.