You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: Cynthia Green here. I would like to book a ticket from DEN to IAD.

ASSISTANT: Sure, can I know your planned travel dates?

USER: My travel dates are Mar 10 and Mar 12.

ASSISTANT: Ok, please let me know your class preference?

USER: There is no class preference but I would like to travel by single connection flight.

ASSISTANT: Any other preferences to be met?

USER: My return time should be in the afternoon and airline preference should be in the normal cost.

ASSISTANT: Ok, please stand by while I check for flights availability.

USER: Sure.

ASSISTANT: I regret to inform you that there were no flights found with your requirements.

USER: No problem, thank you for the help.

ASSISTANT: Thank you for contacting us.