You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, How exactly I can serve you the best today?

USER: I am Andrew Phillips. I want to change an existing reservation due to sudden change in my trip. Can you help me?

ASSISTANT: Sure, we are here to make your work ease. Please wait for a minute.

USER: Ok.

ASSISTANT: Sorry to say that, there is no reservation was found with your good name.

USER: No issue. Thank you.

ASSISTANT: Thank you for reaching us.