You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: My name is Joshua Green.

ASSISTANT: Nice to meet you.

USER: Due to an emergency, my trip is postponed.. Could you help me in changing the reservation?

ASSISTANT: Sure.

USER: Ok.

ASSISTANT: Sorry, no reservation has been found on your name.

USER: That's ok. Thank you for your time.

ASSISTANT: Thank you for visiting us.