You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I want to change my existing reservation. Can you please help me in that?

ASSISTANT: Sure, may I know your name?

USER: Justin Nelson here.

ASSISTANT: We found your reservation, can you please forward your travelling dates?

USER: My trip dates are July 30 to Aug 01.

ASSISTANT: May I know your airport codes?

USER: My preferred airport codes are BOS to CLT.

ASSISTANT: Do you need connecting flight?

USER: I need a direct flight.

ASSISTANT: Do you have any other specifications?

USER: My return should be in the afternoon.

ASSISTANT: Sorry, there are no flights available.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for choosing us.