You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I would like to change my existing reservation, please help me out.

ASSISTANT: Sure, I will help you out. May I Know your name please?

USER: Sure, my name is Gary Walker.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there are no reservations found.

USER: Ok, no issues. Thank you for your information.

ASSISTANT: Thank you for choosing us.