You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you?

USER: I am James Smith want to change my reservation due to prepone of my sister wedding. Can you help me in changing?

ASSISTANT: Sure, please wait for a while.

USER:  Ok.

ASSISTANT: Sorry, there is no reservation found on your given name.

USER: Thank you for your help.

ASSISTANT: Thanks for choosing us.