You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I aid you?

USER: I want to change an existing reservation due to health issues.

ASSISTANT: Sure, may I know your name?

USER: I am Charles Wilson.

ASSISTANT: Ok, please wait a while I will check and get back to you.

USER: Ok.

ASSISTANT: Thanks for waiting, unfortunately there is no reservation found by this name.

USER: Thank you for your response.

ASSISTANT: Thanks for reaching us.