You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how can I aid you?

USER: I am Dennis Wilson. Due to sudden change in my trip to another location, I would like to change my existing reservation. Can you please help me out?

ASSISTANT: Ok, please wait.

USER: Sure.

ASSISTANT:  Sorry, no reservation was found on your name.

USER: Not a problem. Thanks for your quick response.

ASSISTANT: Thank you for availing us.