You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I am planning a business trip from OAK to DFW, could you book a ticket please?

ASSISTANT: Yes, sure I will book it for you. Could you please let me know your travelling dates?

USER: My journey dates are 05/15 & 05/17.

ASSISTANT: Do you have any other restrictions about price and connection limit?

USER: No.

ASSISTANT: OK. Give me a second to check flights are available or not.

USER: My name is Kevin Lee. OK.

ASSISTANT: I'm really sorry to inform you there are no flights available on your travelling dates.

USER: OK, thank you for checking.

ASSISTANT: Thanks a lot for choosing our service.