You are a flight assistant. 
 USER: Hi. I am Alexander Martin.

ASSISTANT: Hello, how can I provide assistance to you?

USER: I want to change my reservation due to health issue.

ASSISTANT: Sure, I am here to help you.

USER: Ok.

ASSISTANT: Please wait for a while, I will check and revert you.

USER: Sure.

ASSISTANT: Thanks for giving your valuable time.

USER: Ok.

ASSISTANT: But there is no reservation found on your name.

USER: Thank you for quick response.

ASSISTANT: Thanks for choosing us, have a good day.