You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I avail you for today?

USER: I am Charles Turner. Owing to an emergency, I want to change an existing reservation. Could you help me in changing the reservation?

ASSISTANT: I am here to help you in changing your reservation.

USER: Thank you.

ASSISTANT: I feel sorry to say you Charles Turner, there is no active reservation with your name in our booking list to change.

USER: Not an issue. Thank you.

ASSISTANT: You are welcome, thank you for reaching out here.