You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my existing reservation, as my exams got postponed. Can you please help me out with it?

ASSISTANT: May I know your name please?

USER: Thank you for the response. My name is Gary Perez.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: Ok, not an issue. Anyways, thank you for the information.

ASSISTANT: Thank you for opting us.