You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how can I help you?

USER: I am Patrick Roberts, I want to change my existing reservation as my exam got postponed.

ASSISTANT: Ok, please wait for a moment.

USER: Ok.

ASSISTANT: I found reservation with your name, please provide me your journey details.

USER: I want to travel to DC- DCA from TX- DFW. I need the ticket within price 500. My travelling dates are from 06/29 to 07/01.

ASSISTANT: May I know your connections limit?

USER: I need a connecting flight.

ASSISTANT: Please wait for a moment, I will check and get back to you.

USER: Ok.

ASSISTANT: Thanks for waiting. Sorry, there is no flights found with your given details.

USER: No problem, thank you.

ASSISTANT: Thanks for choosing us.