You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I guide you for today?

USER: My name is Mark Turner, can you help me to book a flight ticket from SFO to DFW?

ASSISTANT: Can you please share on what dates you are willing to travel?

USER: Ok, please can you book a flight for the dates Dec 30 and Jan 1st?

ASSISTANT: Do you have any airline preferences?

USER: Ok, there is no preferred airlines.

ASSISTANT: Do you have any class preferences?

USER: No.

ASSISTANT: Do you have any other requirements that you are looking for?

USER: Please check for a connecting flight and the departure should be in the evening.

ASSISTANT: Sorry, there are no flights available on your requested dates with your requirements.

USER: Ok, that is no a problem. Thank you for assisting me.

ASSISTANT: Thank you for contacting us, have a nice day.