You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

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

ASSISTANT: Ok, please may I know the dates of your journey as the reservation is found, may I know?

USER: I am planning to travel on Nov 10 and return back on Nov 12.

ASSISTANT: The flight ticket modification need your airport codes to continue, can I know?

USER: My source code is PHX and destination code is DTW.

ASSISTANT: The flight is available with 1 connection limit and the airfare is 300. Can I confirm the ticket?

USER: I afford only 200 for a ticket.

ASSISTANT: Sorry, the flight for that airfare is not available.

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

ASSISTANT: My pleasure, thank you for choosing our agency.