You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Andrew Lopez.

ASSISTANT: How can I help you?

USER: Can you help me to book a connecting flight from OAK to LAS?

ASSISTANT: Let me know your travel dates.

USER: My travelling dates are 12 July and 14 July.

ASSISTANT: Do you have any preference?

USER: I would like to return in the afternoon. I need a direct flight.

ASSISTANT: Sorry, no flights found for your travelling dates.

USER: It's ok, not a problem, thank you.

ASSISTANT: Thank you.