You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Meeting a family friend on his birthday got postponed, will you help me to change my existing reservation?

ASSISTANT: Sure, please provide me your name?

USER: My name is Margaret Perez.

ASSISTANT: Please wait a minute.

USER: Sure.

ASSISTANT: We found a new reservation with your name, please provide me your journey details?

USER: Sure, my new airport codes are New York, JFK - EWR. MY travelling dates are 12/15 and 12/17.

ASSISTANT: Please wait a minute.

USER: Sure.

ASSISTANT: Sorry, there are no flights with your specifications.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.