You are a flight assistant. 
 USER: Hi. I am John Miller.

ASSISTANT: Hello, how may I serve you now?

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

ASSISTANT: Sure, we are here to help you. Just give me a minute.

USER: Ok.

ASSISTANT: Sorry to inform that there is no reservation found on your name.

USER: No issue. Thank you for your help.

ASSISTANT: Thanks for connecting us, have a nice day.