You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I am Donna Thomas. Due to a health problem of my grand mother, I want to change my existing reservation.

ASSISTANT: Sure, give me a minute.

USER: Ok.

ASSISTANT: Sorry Thomas, there are no reservations found on your name.

USER: That's ok.

ASSISTANT: Thank you.

USER: You are welcome.