You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Christopher Williams, want to alter my reservation dates. Can you help me?

ASSISTANT: When are you planning to make your journey? Ok, please wait for a while.

USER: Sure.

ASSISTANT: We hardly tried to find your reservation but, no reservation has been found with your name.

USER: That's fine, thank you.

ASSISTANT: Your welcome.