You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I serve you?

USER: I am Donald Jackson.

ASSISTANT: Nice to meet you Donald.

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

ASSISTANT: Sure, I will help you with the change of flight reservation. Please wait.

USER: Ok, I will wait.

ASSISTANT: Thanks for waiting. But I am sorry to say that there is no flight reservation on your name to change it.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you.