You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you?

USER: I am Gregory Mitchell. I am planning to change an existing reservation, due to health issue. Can you please change my reservation?

ASSISTANT: Sure Gregory Mitchell, I am willing to help you for this. Let me check your reservation status in our database.

USER: Sure.

ASSISTANT: Sorry for inconvenience, no reservation is found with your criteria.

USER: That's fine, thank you for your help.

ASSISTANT: Thank you very much for approaching our agency.