You are a flight assistant. 
 USER: Hello, Melissa Allen here.

ASSISTANT: Hello. Can I know for what support you approach us?

USER: My holiday vacation has been postponed.Can you please help me for cancelling the recent reservation?

ASSISTANT: Yes, I can help you.

USER: Thank you.

ASSISTANT: Sorry, no reservation is found to cancel.

USER: That's really sad. Thank you for your information.

ASSISTANT: Thank you, have a nice day.

USER: Welcome.