You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I support you?

USER: I want to change my existing reservation, due to some health issue. Can you help me?

ASSISTANT: Sure, I am perky to help you.

USER: Ok, not an problem.

ASSISTANT: Can you please let me know your good name to proceed further?

USER: Yes, I am Ronald Jackson.

ASSISTANT: Ok, please wait.

USER: Sure.

ASSISTANT: Thanks for waiting, there is a reservation found on your name. Can you please let me know your updated travelling dates?

USER: Ok, my planned trip dates are on Dec 29 and return on Dec 31.

ASSISTANT: Ok, please help me with your airport codes.

USER: Sure, my airport codes are from BOS to DEN.

ASSISTANT: Is there any other specifications?

USER: Yes, I need a business class.

ASSISTANT: Thanks for providing details, we are sorry to inform you that no flights are available on your journey routes.

USER: Ok, not an problem. Thank you for your information.

ASSISTANT: Thank you for choosing us.