You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello. How can I help you?

USER: Unexpectedly, my trip has been postponed. So I need to change my existing reservation. Please help me out with this.

ASSISTANT: Sure, can I know your name please?

USER: Yes, my name is Mary Parker.

ASSISTANT: Give me a moment Parker.

USER: Sure, take your time.

ASSISTANT: I am sorry Parker, I didn't find any reservation for your details.

USER: Its OK, thank you for the information.

ASSISTANT: You are welcome.