You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how could I assist you now?

USER: I want to change my existing reservation due to postpone of my document verification. Can you help you?

ASSISTANT: Sure, I am happy to help you best. May I know your name to check your reservation?

USER: I am Donald Baker.

ASSISTANT: Thank you.

USER: Ok.

ASSISTANT: We hardly tried to find your reservation but, no active reservation has been registered with us.

USER: Ok, thank you.

ASSISTANT: Thanks for communicating with us.