You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Rachel Walker. Due to my health problem I want to change my reservation dates, can you please help me to change me reservation dates?

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

USER: Thank you.

ASSISTANT: Thanks for waiting patiently. But I regret to inform you that that there is no flight reservation on your name to change it.

USER: Ok, no problem. Thank you so much for your response.

ASSISTANT: Thank you.