You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Karen Hall here.

ASSISTANT: How can I assist you?

USER: I would like to book a ticket from OAK to ORD, can you please help me with that?

ASSISTANT: Ok, may I know your travelling dates?

USER: The travel dates are from 09/19 to 09/21.

ASSISTANT: Sorry, no flights found on your preferable dates.

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

ASSISTANT: Thank you for reaching us.