You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Jennifer Rodriguez.

ASSISTANT: How can I assist you today?

USER: I want to change my existing reservation, can you help me in that?

ASSISTANT: Sure, will you please give me a moment?

USER: Thank you for accepting my request.

ASSISTANT: Your reservation is found. Will you mention your travelling dates please?

USER: My new airport codes are DCA to EWR respectively.

ASSISTANT: Please provide your travelling dates.

USER: My travel dates are 07/11 and 07/13.

ASSISTANT: There is no flights found under your preferable details.

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: Welcome, have a great day.