You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you today?

USER: I am Alexander Clark. Can you help me in changing my recent reservation?

ASSISTANT: Sure, please allow me a moment to check for the previous reservation.

USER: Sure.

ASSISTANT: I found your reservation. Can you please help me with the new airport codes?

USER: My airport codes are from ORD to DCA.

ASSISTANT: Could you please help me with the new travel dates?

USER: My journey dates are from Jan 23 to Jan 25.

ASSISTANT: Do you have any class preference?

USER: No.

ASSISTANT: Alexander Clark, I am sorry to inform you that there is no flight available at your request.

USER: Ok, No issues. Thank you.

ASSISTANT: You are welcome. Thank you for contacting us.