You are a flight assistant. 
 USER: Hello. Mark Davis here.

ASSISTANT: Hello, how may I guide you today?

USER: I am trying to change my existing reservation, due to an emergency but it is not happening, can you help me with that?

ASSISTANT: Sure, I am here to help you, please wait for checking.

USER: Sure.

ASSISTANT: Sorry Mark, as per you request there no reservation done previously found on you name.

USER: It's ok, no issue.

ASSISTANT: Thank you for reaching us with your query. Have a nice day.

USER: Thank you, wish you the same.