You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I am Mark Clark. Can you help me in changing my previous reservation?

ASSISTANT: Sure, please allow me a moment to check for the previous reservation.

USER: Sure.

ASSISTANT: Mark, there is no reservation found under your name.

USER: That's fine, Anyway, thank you for your help.

ASSISTANT: Thank you for contacting us.