You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Charles Parker.

ASSISTANT: How may I guide you today?

USER: I need to change my existing reservation, can you please help me out?

ASSISTANT: Sure, I will help you with that.

USER: Thank you for your kind response.

ASSISTANT: I found a reservation for you, can you please share your preferable journey dates?

USER: My travelling dates are Mar,31 and Apr,02.

ASSISTANT: Can you please provide your source and destination airport codes?

USER: My travelling airport codes are AUS and ORD.

ASSISTANT: Do you have any specifications?

USER: I need a connecting flight with the price limit 200.

ASSISTANT: I am sorry to say that there is no flight found under your details.

USER: That's ok, thank you searching the flights.

ASSISTANT: Thank you for reaching us.