You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you today?

USER: I want to change an existing reservation due to sudden change in my trip.

ASSISTANT: Please can I have your name?

USER: I am John Martin.

ASSISTANT: Please give me a minute.

USER: Ok.

ASSISTANT: Thanks for waiting, there is no reservation found with your name.

USER: Not a problem. Thank you for your service.

ASSISTANT: Have a good day.