You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Nicholas Brown.

ASSISTANT: How may I assist you?

USER: Due to my health problem, I wan to to change my reservation, can you please help me to change my reservation?

ASSISTANT: Sure, I will help you. Please, wait a minute.

USER: Ok, I will wait.

ASSISTANT: Thank you for waiting, there is no reservation found on your name to proceed for modification.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for approaching us.