You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: I am Paul Gonzalez, want to travel from ORD to SFO. Please help me in booking my ticket.

ASSISTANT: Sure, can you please specify me your dates of travel?

USER: My travelling dates are from 11/07 to 11/09.

ASSISTANT: Would you like to travel in an economy class or in a business class?

USER: There is no particular class preference.

ASSISTANT:  Is there any another specifications on your trip, so that I can arrange like that only.

USER: My departing time should be in the evening and my airline preference is normal cost.

ASSISTANT: Sorry, we don't have any flight available for your trip.

USER: It's ok, thank you for your help.

ASSISTANT: Thanks for consulting us.