You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am planning to visit Phoenix with my friends, can you help me with booking?

ASSISTANT: Sure, can I know your name?

USER: I am Donna Nelson.

ASSISTANT: May I know your source and destination airport codes?

USER: My airport codes are DCA to PHX.

ASSISTANT: Can I know your travelling dates?

USER: I will fly on Apr 27 and return on Apr 29.

ASSISTANT: Do you need a stopover in between journey?

USER: No, I need a direct flight.

ASSISTANT: May I know your other preferences?

USER: No.

ASSISTANT: Sorry, there are no flights available on your request.

USER: Ok, no issues. Thank you.

ASSISTANT: Thank you for choosing us.