You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I want to change my recent reservation, due to some health issue. Can you help me?

ASSISTANT: Sure, will you mention your name for checking the reservation status?

USER: Ok, I am David Lopez.

ASSISTANT: There is no reservation found under your name.

USER: That's fine, no problem. Thank you for your help.

ASSISTANT: Welcome, have a great day.