You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: Will you please assist me to change my existing reservation as my plan to meet my friend got postponed?

ASSISTANT: Sure, let me know your name please?

USER: I am William Collins.

ASSISTANT:  Sorry, no reservation found on your given name in our database to change it.

USER: That's ok, no issue. Thank you for your information.

ASSISTANT: Thank you for contacting us.