You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you today?

USER: I want to depart in the evening to meet my cousin, can you help me with booking?

ASSISTANT: Sure, may I know your airport codes?

USER: My airport codes are OAK to IAD.

ASSISTANT: Sure, may I know your travelling dates?

USER: My travelling dates are Apr 09 and Apr 11.

ASSISTANT: On which name shall I reserve flight ticket?

USER: I am William Lee.

ASSISTANT:  Sorry, there are no flights found on given dates.

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your information.