You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you?

USER: I am looking for a flight from LGA to IAH, can you please help me in booking?

ASSISTANT: Sure, I will help you. Please send your travelling dates.

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

ASSISTANT: Do you have any preferences?

USER: I want to return in evening.

ASSISTANT: May I know your name please?

USER: My name is Jack Clark.

ASSISTANT: Sorry, there is no flight available with your requirements.