You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Gary Smith here.

ASSISTANT: Gary, what kind of help are you expecting from our side?

USER: Suddenly, I have some urgent work in my office. So, I want to alter my travelling dates. Can you alter my reservation?

ASSISTANT: Sure, I will help you in changing your reservation.

USER: Thank you.

ASSISTANT: Sorry to inform you Gary, there is no reservation available on your name.

USER: It's ok. Thank you for your valuable time.

ASSISTANT: It's my pleasure.