You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Melissa Collins.

ASSISTANT: How may I help you?

USER: Need your assistance for booking from LAS to DTW. Can you please help me for booking?

ASSISTANT: Sure, tell me your travel dates please?

USER: Sure, my planned journey dates are 30 July and Aug 1.

ASSISTANT: Please wait.

USER: Sure.

ASSISTANT: Thanks for waiting. But I am sorry to say that there are no flights available.

USER: Ok, thank you.

ASSISTANT: Thank you.