You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: Can you please help me to book a ticket from DCA to OAK?

ASSISTANT: Sure, when do you want to start and return on?

USER: I want to depart on Sept 15 and return on Sept 17.

ASSISTANT: Do you prefer a connecting flight?

USER: I need a single connecting flight.

ASSISTANT: Do you have any other requirements?

USER: No.

ASSISTANT: Can I know your good name?

USER: My name is Melissa Adams.

ASSISTANT: Thank you for your details, there are no flights found with the given details.

USER: Ok, thank you for your response.

ASSISTANT: Thank you for your assistance.