You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how can I serve you today?

USER: I am Nicholas Davis and I want to travel from Oakland, CA - OAK on Apr 29.

ASSISTANT: OK, can I know your returning journey details?

USER: My returning details are Washington DC - DCA on May 01.

ASSISTANT: Please wait for a moment, I will check your flight.

USER: OK.

ASSISTANT: Thanks for your patience. Sorry, I did not find any flight on your required details.

USER: OK, Thank you for your service.

ASSISTANT: Thank you, have a nice day.