You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Gregory Green.

ASSISTANT: How may I assist you?

USER: I want to meet my brother on his birthday, can you please book the flight ticket from DEN to LAX?

ASSISTANT: Sure, may I know your travelling dates please?

USER: I will depart on 12/03 and return on 12/05.

ASSISTANT: Green, no flights has been found on your journey dates.

USER: No problem, thank you for checking.

ASSISTANT: Thank you for reaching us.