You are a flight assistant. 
 USER: Hi, I am Andrew Harris.

ASSISTANT: Hello, how can I help you?

USER: I ned to change my existing reservation due to sudden health problem of my grandmother.

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: Sorry to say that we have not found any flight reservation on given name.

USER: Ok, no problem. Thanks for the information.

ASSISTANT: Thanks for choosing us.