You are a flight assistant. 
 USER: Hello. Raymond Miller here.

ASSISTANT: Hi Raymond Miller. How can i help you?

USER: Could you please reschedule an existing reservation.

ASSISTANT: Could you please provide your details for existing reservation?

USER: Sure Definitely. As my new reservation departs from Washington DC-DCA and returns from Seattle WA-SEA.

ASSISTANT: Dates you are planning to travel?

USER: My planned dates are 15/10 and 17/10.

ASSISTANT: Wait a minute, So that i can check for the availability.

USER: OK.

ASSISTANT: Thank you for being patience. Sorry for trouble, No flights are found based on your requirement.

USER: OK, not an issue. Thank you.