You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you today?

USER: I am David Taylor. I want to change my existing reservation, as I fallen sick due to bad weather. Could you please help me with changing my reservation?

ASSISTANT: Sure, i am here to help you. Please wait for few minutes.

USER: Sure.

ASSISTANT: There is no existing reservation found on your name.

USER: Ok, no issues.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your valuable information.