You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I want to change my reservation, due to examination schedule postponed. Can you please help me?

ASSISTANT: Sure, may I ask you for your name please?

USER: My name is Katherine Miller.

ASSISTANT: Give me a moment.

USER: Sure, take your own time.

ASSISTANT: Katherine Miller. I regret to inform that there is no reservation by your name.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for contacting us.