You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am Gary Green, want to alter my recent reservation due to some emergency. Please help me out with that.

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: Sorry, no reservation found on your name to change your reservation.

USER: It's ok, thank you for your help.

ASSISTANT: Welcome, have a nice day. Thank you for choosing us.