You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Christine Moore here.

ASSISTANT: Moore, how may I guide you?

USER: I am a tennis player, I have to play in a match at Denver, please book my ticket from Houston.

ASSISTANT: Sure, can you please share me your source airport code and destination airport code?

USER: My airport codes are HOU and DEN.

ASSISTANT: When would you like to travel?

USER: My itinerary dates are 08/13 and 08/15.

ASSISTANT: There is a flight with Delta airlines and the ticket fare is 500. Would you like me to proceed for booking?

USER: I can afford 200 for my ticket.

ASSISTANT: Ok. Sorry for inconvenience,  there is no flight available with your requirement.

USER: No problem, thank you.

ASSISTANT: Thank you very much for contacting us.