You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I serve you?

USER: I am Melissa Harris. I am planning to visit Museum of Nature and Science at Denver, could you please help me with booking a flight ticket from OAK to DEN?

ASSISTANT: Sure, we are perky to assist you. Can I know your travelling dates?

USER: I would like to depart on Mar 26th and return on Mar 28th.

ASSISTANT: Do you have any class preference?

USER: I am comfortable with any class.

ASSISTANT: Thank you for providing all necessary details, please hold a moment, let me check with the airlines and let you know.

USER: Sure, take your time.

ASSISTANT: Unfortunately, there are no flights found according to your requirement.

USER: Ok, I will find an another alternate way to complete my trip.

ASSISTANT: Thank you for choosing us.

USER: Anyways, thank you for the information.