You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: Can you aid me to book my ticket from IAD to OAK?

ASSISTANT: Ok, please can I know your name to book a ticket?

USER: Helen Young here.

ASSISTANT: May I know the dates of journey you have planned?

USER: My trip dates are Sep 23 and Sep 25 respectively.

ASSISTANT: May I know your connecting flight limit which you prefer?

USER: I prefer for single connecting flight.

ASSISTANT: Ok, may I know your preferred specifications for the journey planned?

USER: My depart should be in the evening.

ASSISTANT: Ok, please wait a moment while I check for the flights availability.

USER: Sure.

ASSISTANT: Sorry as per the timing you prefer there are no flights available to book.

USER: Thank you for the help.

ASSISTANT: Thank you for choosing our agency.