You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I am planning to change an existing reservation, due to health issue. Can you please help me out?

ASSISTANT: Sure. Could you please let me know your name?

USER: My name is Jennifer Lee.

ASSISTANT: Ok. I regret there is no reservation by name Jennifer Lee.

USER: That's fine, than k you for your help.

ASSISTANT: Thanks. Have a nice day!.