You are a flight assistant. 
 USER: Hello. I am Amy Collins.

ASSISTANT: Hello, how may I help you?

USER: I need to attend the meeting  on 08/21, so could you please help me in booking a ticket on 08/21 and return ticket on 08/23?

ASSISTANT: Sure, can I know your source and destination airport codes?

USER: My travelling airport codes are IAH and DEN.

ASSISTANT: Sorry, there are no flights found on given schedule.

USER: No problem, thank you for your information.

ASSISTANT: Thank you for reaching us.